404 pisces. 



nerves from the brain are in number [nine pairs 1 , including] the olfac- 

 tory and optic. The nerves seem to grow larger as soon as they have 

 passed through the skull. There is a white mucus in the ear 2 , instead 

 of bone, as in the cod, &c. : this is partly mucus, and partly calcareous 

 earth, as it is partly soluble in an acid. 



On the inside of the anus, just on the outside of the ring, there are 

 two protuberances like flaccid nipples : these are two openings which 

 communicate with the general cavity of the belly. This structure will 

 allow of water to pass out, but none to pass in 3 . There is no ' sound ' 

 [air-bladder]. How this fish contrives to keep itself of the same specific 

 gravity with the water I do not know. Sea- water is heavier than fresh. 



Galeus, or Carcharias. 



The shark, the jaws of which I had of Mr. Bowater 4 , was 11 feet 

 from the snout to the end of the tail ; and, when killed, had several 

 young in its belly. It had also a brickbat in the cavity of the stomach ; 

 it therefore must have the power of regurgitation. 



The Dog-fish [Spinax acanthias, Cuv. 5 ] . 



There are two fins on the back, one near the middle of the fish, the 

 other near the tail : upon the anterior edge of each fin stands a sharp- 

 pointed thorny substance : that on the posterior fin is the largest. By 

 these it defends itself, and perhaps assists in tearing its food ; for, when 

 anything offends its head, by laying hold of it, or if it be hooked, it 

 immediately turns round its tail and darts this horny spike into it [the 

 offending object] and tears it away. 



There are two rows of teeth in the lower jaw, and three in the upper. 

 The rows in one (when the mouth is shut) pass in between the rows of 

 the other. The teeth stand obliquely with their points turned back, 



1 [The homologue of the gustatory nerve of mammals is wanting ; but the glosso- 

 pharyngeal has an origin distinct from that of the par vagum.] 



2 [Hunt. Prep. Phys. Series, No. 1574.] 



3 [Dr. Andrew Smith informed me that he had found a quantity of sea-water in 

 the abdomen of sharks which he had dissected at the Cape. 



Qu. Does it enter to defend the viscera from external pressure ? or to compensate 

 for the want of power or facility in the abdominal parietes to accommodate them- 

 selves to changes in the dimensions of the contained viscera, the water entering, for 

 example, after the evacuation of the ova or semen ? But the fact should, first, be 

 expressly sought for and determined by analysis.] 



4 [In the Hunterian Osteological Collection are preserved the jaws of Galeus 

 ferox, No. 405, and of Carcharias macropterus, No. 417, either of which answer to 

 the dimensions above given.] 



5 [Parts of the skeleton of this fish form Nos. 390 and 391, Hunt. Osteol. Series.] 



