In addition to an enormous body of new information chiefly on the shoulder girdle, the alar muscles and the nerve plexuses of birds, this work contained a critical and descriptive summary of practically the whole pre-existing literature on the structure of birds, and it is hardly necessary for the student of ornithology to refer to earlier literature at first hand.
Of Thecidiosmilia, two septa, corresponding to the mainand counter-septa of Streptelasma, are first formed, then two alar septa, and afterwards the remaining septa, the latter taking on a generally radial arrangement, though the original bilaterality is marked by the preponderance of the main septum.
M, Main septum; c, counter septum; t, t, alar septa.
The secondary septa show a regular gradation in size, and, assuming that the smallest were the most recently formed, it will be noticed that in the chief quadrants the youngest septa lie nearest to the main septum; in the other quadrants the youngest septa lie nearest to the alar septa.
The remaining septa are so disposed that in the quadrants abutting on the chief septum they converge towards that septum, whilst in the other quadrants they converge towards the alar septa.
In this coral the calicle is divided into quadrants by four principal septa, the main septum, counter septum, and two alar septa.