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Show 1886.] POINTS IN THE ANATOMY OF CAPRIMULGIDJE. 151 The intrinsic muscles of the syrinx are inserted on to the fifteenth or sixteenth bronchial ring, much lower down therefore than in Batrachostomus; the first two bronchial rings are complete; the following fourteen are semirings, but are wide, firmly united to each other, and ossified; the membrana tympaniformis forms the inner wall of this and of the following section of the bronchus. The posterior section of each bronchus, as in Batrachostomus, is formed of slender cartilaginous semirings separated by wide membranous intervals. As far as the structure of the syrinx is concerned Steatornis stands alone; Podargus and Batrachostomus are closely similar to each other, and are transitional between such genera as Caprimulgus and Steatornis; the insertion of the intrinsic muscles so far down the bronchus, and the similarity between the anterior rings of the bronchus and those of the trachea, is evidently an approach in structure to the bronchial syrinx of Steatornis. AZgotheles resembles Batrachostomus more closely than it does Caprimulgus, but the number of bronchial semirings which intervene between the trachea and the insertion of the syringeal muscles is still further reduced. Caprimulgus, Chordeiles, and Nyctidromus are very closely allied in the structure of their syrinx, which is tracheo-bronchial, and shows no approach to the bronchial syrinx of Steatornis, as do the syringes of Podargus, Batrachostomus, and (to a very much less extent) AUgo-theles. The arrangement of the genera of Caprimulgidae, as indicated above by the structure of their syrinx, is, I believe, in accord with the opinion of most ornithologists. With regard to other structural characters, the following notes upon certain of the viscera and muscles appear to be worth recording. Visceral Anatomy. The intestines of the Caprimulgidae are furnished with caeca, with the exception of those of A^gotheles. Mr. Forbes has left a M S. note to this effect, and 1 cannot find any trace of caeca in the spirit-preserved specimen of the last-mentioned form. In all the genera the left lobe of the liver is rather the smaller, and a gall-bladder is present save in Chordeiles1. The air-sacs in one specimen of Steatornis were rather peculiar in structure. The points in which they were found to differ from other birds are in the posterior intermediate air-sac. This sac on both sides of the body is considerably larger than the preceding anterior intermediate sac, and is furnished with two principal ostia placed near to the external border of the lung. These r pertures have a different position in relation to each other on either side of the body; in the right lung these apertures do not both open into the posterior intermediate air-sac as they do on the left side of the body ; the most anterior of the two ostia opens into a small wedge-shaped air-cell, which is completely separated by septa both from the posterior 1 Garrod MS. |
