252 NATURAL SCIENCE April, 



primitive than the caudal of the most generalised of modern sharks, 

 inasmuch as its cartilaginous supports extend from the body-terminal 

 as far as the extreme margin of the fin, and that the hypural region of 

 the dorsal lobe is entirely without cartilaginous or other supports 

 (save, perhaps, actinotrichia), precisely as in embryonic protocercy. 



(e.) Reproductive System. — Cladoselache appears to have been lacking 

 in claspers — a condition unknown among recent Elasmobranchia, 1 

 and exceedingly significant, therefore, in this ancient shark. The 

 general character of the hinder margin of the ventral fin seems at 

 once to preclude the presence of intromittent structures ; in over a 

 dozen examples of well-preserved pelvic fins nothing has been found 

 which could possibly be interpreted as relating to these organs. It 

 accordingly follows, with more than fair probability, that this primaeval 

 shark had not evolved the highly-modified reproductive methods of 

 its living kindred, but, like ganoid and lung-fish, fertilised its eggs 

 at the moment of extrusion. In this event, it would seem exceedingly 

 probable, judging by many analogies, that the number of the eggs 

 deposited must have been considerable ; they might accordingly have 

 been small in size and not over rich in their yolk-supply. 



(/.) Organs of Sense. — The position of the olfactory capsule has 

 been outlined in many specimens ; the position of the external narial 

 openings appears to have been dorsal, and the present writer believes, 

 from the study of a well-preserved mouth-margin, that its conditions 

 in general resembled those of Notidanidae. Well-marked labial carti- 

 lages must have been absent, and there is certainly no evidence in 

 support of the cirrhostomial theory (Pollard) to be derived from 

 Cladoselache. No lateral flap-covered canal appears to have united 

 the cavities of mouth and nose. 



The eye capsule was scarcely larger, proportionately, than in 

 recent sharks. Its dermal investment by concentric rings of enlarged 

 shagreen plates has already been noted by Jaekel and others. The 

 present writer notes that this method of the protection of the eye 

 capsule may well be regarded as a primitive specialisation, inasmuch 

 as the integument is functioning in the defence of the delicate optic 

 sense-bulb, instead of the underlying tissue ; in other words, the 

 sclerotic of this ancient form may not have assumed its protective 

 characters. 



The lateral line has been traced as a well-defined space between 

 rows of shagreen denticles, and it follows, therefore, that an open 

 sensory groove persisted, as in Chlamydoselache. In the fossil form, 

 however, judging from the characteristic tail structure, this condition 

 could not have been due to bathybial environment. 



In view of the structural characters which have just been 

 summarised, it seems to follow that in Cladoselache has been 

 discovered an Elasmobranch of an exceedingly primitive nature. 



1 This condition does not occur in Lamargus, as Professor Lutken at first believed. 



