In rare cases the right and left preacetabular blades fuse with each other above the spinous processes.
In this family there is often a marked divergence between the sexes; the terminal antennal segments are larger in the male than in the female, and the males may carry large spinous processes on the head or prothorax, or both.
The oesophagus expands into a curious gizzard, which is armed internally with large horny processes, some broad and thick, others spinous, fitted to act as crushing instruments.
Their scales are generally rough and spinous; but otherwise they possess no strikingly distinguishing peculiarity, unless the loose skin of their throat, which is transversely folded and capable of inflation, be regarded as such.
- Similar to Encephalartos except in the presence of a spinous projection from the swollen distal end of the carpels.
Spinous processes on the apex of the carpels.
In rare cases the pinnae of cycads are lobed or branched: in Dioon spinulosum (Central America) the margin of the segments bears numerous spinous processes; in some species of Encephalartos, e.g.
In Ceratozamia the broad petiole-base is characterized by the presence of two lateral spinous processes, suggesting stipular appendages, comparable, on a reduced scale, with the large stipules of the Marattiaceae among Ferns.
One of the best known examples is the Chinese juniper (Juniperus chinensis), in which branches with spinous leaves, longer and more spreading than the ordinary adult leaf, are often found associated with the normal type of branch.
The spinous processes of the anterior thoracic region are high and compressed.
With three spinous pads on the legs, B (After Sedgwick.) FIG.
A and feet with two primary papillae on the anterior side and one on the posterior side; outer jaw with one minor tooth at the base of the main tooth, inner jaw with no interval between the large tooth and the series of small ones; last fully developed leg of the male with enlarged crural gland opening on a large papilla placed on its ventral surface; coxal organs absent; the nephridial openings of the 4th and 5th pairs of legs are placed in the proximal spinous pad.
P. tholloni, Bouvier, (Equatorial West Africa [Gaboon]), shows some neotropical features; there are 24 to 25 pairs of legs, the genital opening is between the penultimate legs, and though there are only three spinous pads the nephridial openings of the 4th and 5th legs are proximal to the 3rd pad, coxal organs are present, and the jaws are of the neotropical type; the oviducts have receptacula seminis.
- With three to five spinous pads on the legs, nephridial opening of the 4th and 5th legs usually proximal to the 3rd pad, and feet either with two primary papillae on the anterior side and one on the posterior, or with two on the anterior and two on the posterior; outer jaw with small minor tooth or teeth at the base of the main tooth, inner jaw with diastema.
- With 22 to 24 pairs of claw-bearing legs, with three spinous pads on the legs, and nephridial openings of legs 4 and 5 (sometimes of 6 also) on the proximal pad; feet with one primary papilla on the anterior, one on the posterior side, and one on the dorsal side (median or submedian); outer jaw with a minor tooth, inner jaw without diastema; crural glands absent; well-developed coxal organs absent.
With 23 to 25 pairs of claw-bearing legs, four spinous pads on the legs, and nephridial openings of legs 4 and 5 in the middle of the proximal pad or on its proximal side; feet with two primary papillae, one anterior and one posterior; outer jaw with two, inner jaw with two or three minor teeth at the base of the main tooth, separated by a diastema from the row of small teeth; crural glands present in the male only, in the two pairs of legs preceding the generative opening; coxal glands present.
In these cases the peduncles may persist and may even be modified into spinous organs of defence.