964 MRS. O. A. MERUITT HAWKES ON THE [Dec. 11, 



.suggestion is perhaps confirmed by finding one such lateral branch, 

 nearly 1'5 cm. in length, in the tail-region of another specimen. 



The Lateral canal runs in the usual position from the head to 

 the end of the tail, and is noteworthy owing to the fact that only 

 the first inch is closed. The neuromasts occur at much more 

 irregular intervals than is the case in the head-canals. In all the 

 specimens examined there is a tendency in the region of the 

 dorsal fin (text-fig. 140, Y) to a departure from a straight line. 

 In two specimens this tendency produced four distinct undulations. 

 .Similar undulations have been found in Callorhynchus (Cam. Nat. 

 Hist., Fishes, T. W. Bridge, fig. 269, p. 470). In other cases the 

 canal undulated slightly. No explanation of this phenomenon 

 can be oifered. This same region had on one side, in one specimen, 

 a complete break of 5 mm. There was in this space no trace of 

 canal or of covering scales. Garman also found curves and breaks 

 on this canal in the tail-region. 



The conclusion arrived at from these facts is that the 

 lateral line system of Chlamydoselachus is primitive as regards 

 (1) the open condition of a portion of the canals ; (2) the cutaneous 

 rather than subcutaneous position of the canals ; (3) the entire 

 absence of tubules in many places. In the occipital and hyo- 

 mandibular regions, however, the system tends to a considerable 

 complexity. Again there are indications, in the occipital and 

 lateral canals, of either a vestigial or rudimentary complexity. 



The innervation is an additional difiiculty in the determination 

 of the relations of this system. The lateralis branches of the 

 Facialis present no difiiculty, but if there are jiroved to be fibi-es 

 of the ninth nerv^e innervating a few lateralis sense-organs, these 

 must be regarded as an additional proof of the comparatively 

 primitive nature of the system. The lateralis nerves in oiigin 

 were probably related morphologically to a number of segments, 

 and later became concentrated into the main trunks of the Facialis, 

 Auditory and Vagus nerves. The fact that Chlamydoselachus has 

 four lateralis roots, two for the buccalis, one for the external 

 mandibularis, and one for the r. lateralis vagi, probably indicates a 

 comparatively piimitive condition for this system. 



C. The Ampulla of Lorenzini. 



In Ohlamydoselachus the anatomy and the arrangement of the 

 ampullae difter from those of the higher Elasmobranchs. 



The anterior, latero-dorsad surface of the head, from the level of 

 the eye to the end of the snout, is covered by ampullary openings 

 which are divided into two groups by the Supra- orbital canal. 

 The ampulla? of this whole region are innervated by the r. super- 

 ficialis ophthalmicus YII. and are therefore probably homo- 

 logous with the usual supra-orbital group of ampullse. This group 

 may, in Chlamydoselachus also, be called the supra-orbital. 



A second group of ampullae is found between the post-orbital 

 portion of the infra- orbital lateral line canal and the spiracle. It 



