74 PHYSIOLOGICAL SERIES. 



responding development either of the fore-brain or of an 

 olfactory bulb; in fact it is stated that an olfactory bulb is 

 absent. This marked disproportion in development between 

 the olfactory nerves and the cerebrum, with the apparent 

 absence of definite olfactory bulbs, suggests that the nerves, 

 although evidently to a great extent fibrous, probably also 

 have the nature of olfactory centres ; it should be noticed 

 in this connection that shortly before entering the cerebrum, 

 'each olfactory nerve undergoes a very perceptible enlarge- 

 ment. The poor development of the optic parts of the 

 brain are probably to be accounted for by the deep habitat 

 of this Shark. The brain occupies only a small part of 

 the -paciuus cranial cavity. 



This preparation is from a fish caught off the coast of 

 Cornwall. 6. C. 1311s a. 



Presented by F. Buckland, Esq. 



Jackson & Clarke, Journ. Anat. & Physiol., vol. x. 1876, 

 p. 76. 



D. 71. Part of the skull of a Spiny Dog-fish (Acantldas vulyaris) 

 with the brain exposed from the dorsal and ventral aspects. 

 Thi- i> a simple brain like the preceding specimen, but 

 shows certain differences that foreshadow more pronounced 

 features in the relatively complex brains of higher Sharks; 

 such are a pair of indistinct rounded eminences upon the 

 dorsal surface of the fore-brain at its hinder end, and the 

 deepening of the transverse cerebellar furrow. The median 

 indentation of the fore part of the cerebrum is strongly 

 marked and terminates on the dorsal surface in a rounded 

 j.it a nutritive foramen of very constant occurrence among 

 Blftimobranohi, The olfactory peduncles are slender and of 

 moilerate length with >mall olfactory bulbs ; on the oilier 

 hand, the visual organs ami optic lolics are very strongly 

 leM-h.pe.1. The lohi inferiores are also well marked and 

 oval in form. The medulla does not differ in any important 

 from that of previously deseribed primitive forms. Its 

 cavity is exposed on the v\\\\ >i<le. 



D. 72. Part of the cranium of a Spotted Dog-fish (Scyllium 

 \\ith the brain in situ. This brain, in comparison 



