OF BAL^XOPTERA MXJSCULUS. 227 



runs into the bone at the junction of the anterior and middle divisions. It is the continua- 

 tion of the aqueductus Fallopii. Beside this one is quite a minute groove apparently for a 

 small vessel or nerve. 



The anterior portion is a three-sided pyramid pointing nearly straight forward. The in- 

 ner side is rough ; the others tolerably smooth. There is a considerable prominence near 

 the base on the outer aspect. 



The middle or labyrinthic division is the most important, as it contains the vestibule, 

 the cochlea and the semicircular canals. It is conical in shape, the apex being perforated 

 by two foramina of equal size — about one-half inch in diameter — the aqueductus Fallopii 

 anteriorly and the internal auditory meatus posteriorly. In this respect it is very different 

 from that of the B. rostrata, as described by Drs. Carte and Macalister. The aqueductus 

 perforates the bone, and changing its course, reappears at the base of the labyrinthic portion 

 and is continuous with the groove in the posterior division. A small canal opens on the an- 

 terior aspect of the labyrinthic part. It is found to open into the aqueduct, and is probably 

 for the passage of the chorda tympani. Towards the posterior edge of the upper surface 

 there is a deep funnel-like depression, which, as far as I can ascertain, has no opening at its 

 lower end. Directly internal to this, guarded at its orifice by a bony spine, is the aqueduc- 

 tus cochleae, which opens mto the scala tympani a little inside the fenestra rotunda. I 

 have found nothing to represent the aqueductus vestibuli. The fenestra ovalis is situated 

 in the depths of the cavity of the tympanum, and is surrounded by a raised wall. The 

 fenestra rotunda is, as is usual in Cetacea, considerably removed from the ovalis, being 

 posterior and external to it. 



The cochlea was chiselled out by removing with great labor a part of the internal aspect 

 of the bone. It consists of nearly 2 1-3 turns, which is more than I have found described 

 for any whale — the B. rostrata having two turns, according to Carte and Macalister, and 

 2 13-360, according to Hyrtl. AVith regard to position, the modiolus appears to point 

 very nearly downward when the bone is in place. The scala tympani, as usual in Mam- 

 malia, is at first larger than the scala vestibuli, and then smaller. Where the preparation 

 has been slightly broken it is easy to see the spiral canal formed by a cavity in the lamina 

 spiralis described by Hyrtl as peculiar to Cetacea. There is no trace of a lamina spiralis 

 secondaria. The bone was exceedingly brittle and the preparation very difficult, so that 

 the semi-cu-cular canals were quite destroyed — the only description I can offer of them is 

 that they were very minute. 



Classification. 



From this description there can be no doubt that this is a specimen of the Physalus an- 

 ticjuornm of Gray, or the BaJanoptera musculus of authors and most recently of Van Ben- 

 eden. The classification of the latter has been chosen as the most "conservative," and the 

 one allowing the greatest scope to individual variation. Whether the Darwinian hypothe- 

 sis be accepted or not, the opinions of Mr. Darwin on individual differences and on the 

 formation of species and varieties are entitled to the greatest respect, and the following 

 quotations from the second chapter in his '-Origin of Species" are very much to the point : 

 ''These individual differences generally affect what naturalists consider unimportant parts ; 

 but I could show, by a long catalogue of facts, that parts which must be called important, 



