Eventually, when the right and left feet of the coracoids overlap each other, the anterior sternal spine contains a foramen.
The large and heavy crop has caused a unique modification of the sternal apparatus.
Without sternal keel.
Division Odontolcae.-Marine, flightless, without sternal keel.
For example, the con Head muscles y traction of the tergo A 's sternal muscles, connect r.
Moreover, the author goes on to remark that in adult birds trace of the origin of the sternum from five centres of ossification is always more or less indicated by sutures, and that, though these sutures had been generally regarded as ridges for the attachment of the sternal muscles, they indeed mark the extreme points of the five primary bony pieces of the sternum.
But Merrem, who subsequently communicated to the Academy of Berlin a more detailed memoir on the " flat-breasted " birds, 3 was careful not here to rest his divisions on the presence or absence of their sternal character alone.
Notice has next to be taken of a Memoir on the Employment of Sternal Characters in establishing Natural Families among Birds, which was read by De Blainville before the Academy of Sciences of Paris in 1815, 5 but not published in full for more than five years later (Journal de physique.
This is a very disappointing performance, since the author observes that, notwithstanding his new classification of birds is based on a study of the form of the sternal apparatus, yet, because that lies wholly within the body, he is compelled to have recourse to such outward characters as are afforded by the 1 From carin g, a keel.
3-93) the " Recherches sur l'appareil sternal des Oiseaux," which the precept and example of his master had prompted him to undertake, and Cuvier had found for him the means of executing.
We have already seen that De Blainville, though fully persuaded of the great value of sternal features as a method of classification, had been compelled to fall back upon the old pedal characters so often employed before; but now the scholar had learnt to excel his teacher, and not only to form an at least provisional arrangement of the various members of the Class, based on sternal characters, but to describe these characters at some length, and so give a reason for the faith that was in him.
But the latter used this privilege wisely and well-not, after the manner of De Blainville and others subsequent to him, relying solely or even chiefly on the character afforded by the posterior portion of the sternum, but taking also into consideration those of the anterior, as well as of the in some cases still more important characters presented by the pre-sternal bones, such as the furcula, coracoids and scapulae.
He of course knew the investigations of L'Herminier and De Blainville on sternal formation, and he also seems to have been aware of some pterylological differences exhibited by birds - whether those of Nitzsch or those of Jacquemin is not stated.
On the whole the remarks of this esteemed author do not go much beyond such as might occur to any one who had made a study of a good series of specimens; but many of them are published for the first time, and the author is careful to insist on the necessity of not resting solely on sternal characters, but associating with them those drawn from other parts of the body.
Important as are the characters afforded by the sternum, that bone even with the whole sternal apparatus should obviously not be.
That the palatal structure must be taken into consideration by taxonomers as affording hints of some utility there can no longer be a doubt; but perhaps the characters drawn thence owed more of their worth to the extraordinary perspicuity with which they were presented by Huxley than to their own intrinsic value, and if the same power had been employed to elucidate in the same way other parts of the skeleton - say the bones of the sternal apparatus or even of the pelvic girdle - either set might have been made to appear quite as instructive and perhaps more so.
Although loss of flight (correlated with more or less reduction of the wings and the sternal keel, and often compensated by stronger hind limbs) has occurred, and is still taking place in various groups of birds, it is quite impossible that a new Ratite can still come into existence, because the necessary primitive substratum, whence arose the true Ratitae, is no longer available.
The various comparisons previously made between the structure of Limulus and the Eurypterines on the one hand, and that of a typical Arachnid, such as Scorpio, on the other, had been vitiated by erroneous notions as to the origin of the nerves supplying the anterior appendages of Limulus (which were finally removed by Alphonse Milne-Edwards in his beautiful memoir (6) on the structure of that animal), and secondly by the erroneous identification of the double sternal plates of Limulus, called " chilaria," by Owen, with a pair of appendages (7).
Their minute structure is closely similar in the two cases; the leaf-like plates receive blood from the great sternal sinus, and serve as respiratory organs.
That is neces sarily a blood-holding structure and is obliterated and fused with soft tissues of the sternal region so that the lamellae cannot be detached and presented as standing out from it.
It appears not improbable that the sternal plates wedged in between Fll '` vu...
The unsegmented dense chitinous sternal plate of the metasoma (XIII to XVIII) is not removed.
This has not been demonstrated by an actual following out of the development, but the position of these pieces and the fact that they are (in Limulus) supplied by an independent segmental nerve, favours the view that they may comprise the sternal area of the vanished praegenital somite.
Palamnaeus indus, de Geer, to show the arrangement of the coxae of the limbs, the sternal elements, genital plate and pectens.
--Diagrams of the meta-sternite st, who showed that with genital operculum op, and the first lamellithe statements of gerous pair of appendages ga, with uniting von Graber were sternal element st of Scorpio (left) and Limulus erroneous, and (right).
- Diagram to show the way in which an outgrowing gill - process I bearing blood-holding lamellae, may give rise, if the sternal body wall sinks inwards, to a lung-chamber with air-holding lamellae.
A is the condition of insinking of the sternal surface and consequent enclosure of the lamelligerous surface of the appendage in a chamber with narrow orifice - the pulmonary air - holding chamber.
The entosternite was probably in origin part of the fibrous connective tissue lying close to the integument of the sternal surface - giving attachment to muscles corresponding more or less to those at present attached to it.
Tsm l, Tergo-sternal muscle (labelled dv in fig.
Tsm 4, Tergo-sternal muscle of the fifth mesosomatic somite.
Tsm s, Tergo-sternal muscle of the enlarged first metasomatic somite.
In these batrachians the pectoral arch falls into two distinct types - the arciferous, in which the precoracoid (+clavicle) and coracoid are widely separated from each other distally and connected by an arched cartilage (the epicoracoid), the right usually overlapping the left; and the firmi- sternal, in which both precoracoid and coracoid nearly abut on the median line, and are only narrowly separated by the more or less fused epicoracoids.
(7) The endopoditic ramus is greatly enlarged and flattened, without or with only one jointing, the corm (basal segment) is evanescent; often the plate-like endopodites of a pair of such appendages unite in the middle line with one another or by the intermediary of a sternal up-growth and form a single broad plate.
In conformity with these reductions the breastbone of the moas is devoid of any coracoidal facets; there is no trace of a keel, and the number of sternal ribs is reduced to three or even two pairs.
P, The tergal stigmata of the tergo-sternal muscles.
- Thelyphonus sp. Ventral view of the anterior portion of the body to show the three prosomatic sternal plates a, b, c, and the rudimentary sternal element of the praegenital somite; opisth 1, first somite of the opisthosoma.
- Prosoma longer than wide, its sternal area very narrow, furnished with a large prosternal and metasternal plate, and often with a small mesosternal sclerite.
Sternal area broad, with prosternal, two mesosternal, and metasternal plates, the prosternum projecting forwards beneath the coxae of the 2nd pair of appendages.
St 1, Anterior sternal plate of the prosoma.
S1 2, Posterior sternal plate of the prosoma.
Opistho I, First somite of the opisthosoma; opistho 2, second do.; g, genital aperture; 1, edges of the lamellae of the lung-books; m, stigmata of tergo-sternal muscles.
(Original drawing by Pocock.) freely movable; claw free or fused; basal segments of 4th and 5th pairs widely separated by the sternal area; appendages of 3rd pair with all the segments except the proximal three, forming a manyjointed flagellum.