BRAIN. 



193 



upper end of the clavicle is a bony rod, the post-clavicle. There 

 is no infraclavicle. The skeleton of the fin consists of usually 

 five basal ossified somactids which are articulated with the 

 coraco-scapula, and of a row of small cartilaginous pieces 

 representing distal somactids. These are followed by the 

 dermotrichia, the anterior of wliich is continuous with the an- 

 terior of the basal somactids. 



The pelvic girdle is always absent, its place being taken by a 

 large osseous basal somactid, commonly called the basiptery- 

 gium ; to this are attached a few small, partly bony, distal 

 somactids, which carry the dermotrichia. 



The brain * of Teleosteans presents the following features. 



Fig. 113. — Median longitudinal vertical section through the brain of the trout (from Gegen- 

 banr, after Rab-Kiickhard). Aq aqueductus sylvii; Bo olfactory lobe; Cbl cere- 

 bellum; Cc central canal of spinal cord; Ccn anterior commissure; Cho. optic ner\-es; 

 C'i inferior commissure; G';> pineal body; Hi/, Sy- hj^pophysis; J infundibulum; Nol 

 olfactory nerve; Pa pallium; pf vehmi transversum; Sv saccus vasculosus; Tco pia 

 mater on the dorsal side of the mid-brain ; Tl dorsal wall of mid-brain between the two 

 optic lobes; /r crossing of the fibres of the fourth nerve ; Fc vah-ula cerebelli; Fcm ven- 

 tricle of the cerebnim ; Fg fourth ventricle; T'< third ventricle. 



(1) The olfactory lobes are usually much elongated and 

 slender; they are swollen at their free ends against the nasal 

 capsules and at their origin. The cerebral ventricle is continued 

 into the swollen base.f 



* Rabl-Riickhard, Das Grosshini der Knochenfische, etc., Arch, f, 

 Anat. und Phys., Anat. Abt., 1883, p. 279-322. E. Baudelot, Recherches 

 sur le systeme nerveux des Poissons, Paris, 1883. A. Schafer, Die morphol. 

 u. hist. Entwick. d. Kleinhirns der Teleostei, Morph. Jahrb., 21. 



t There seems to be some difference of opinion as to whether these basal 

 swellings alone constitute the olfactory lobes, the slender prolongations 

 being only olfactory nerves. It has been suggested that in some fishes, 

 e.g. Salmon, this is the case, whereas in others, e.g. Cj^rinoids, the 

 whole elongated structure is also part of the olfactory lobe. 



Z— II o 



