DAVIS: NOTE ON CHLAMYDOSELACHUS. 
Ill 
natr.ially between these two g-enera. But its relationship with 
existing forms is considered of minor importance when compared 
with its *' close aflSnity to the genus Cladodus." From first 
mentioning- the genus Mr. Garman has insisted on its resemblance to 
Cladodonti. *'A further study of both extinct and recent forms 
enables me to speak still more positively in asserting that Chlamy- 
doselachus is a Cladont. As shown in the description above, some 
of its teeth are so characterized as to make it imperative, if these 
teeth are alone considered, that the species should be placed in the 
genus Cladodus of Agassiz, and nearer than almost an}^ of the fossil 
forms to his t3'pe C. mirabilis.'' ^ 
It remains now to be considered w^hether the teeth of Chlamy- 
doselachus are so closely i-elated to those of Cladodus as to warrant 
their inclusion in the same group. The possible relationship of 
Ctenacanthus and Cladodus being for the moment disregarded, the 
teeth comprised in the Cladodont family exliibit a very considerable 
variety of form, but there are certain characters which appear in all, 
these may be defined in the broadly-expanded, horizontal, thick 
osseous base, semicircular behind, truncated in front : from the 
truncated margin rise a varying number of sharp conical points or 
denticles at right angles to the base. The median cone is the y 
largest and the two external secondary ones are larger than the 
intermediate ones where such exist. Cladodus mirabilis, Agass., 
may be taken as the type of its genus. It is a large powerful tooth, ^ 
with strong central cone and two or three secondary ones on each 
side, the posterior expansion of the base is probably larger in this 
species than in any other. In the Enniskillen collection now at the 
Natural History 'Museum, in London, there are two species of 
Cladodus, named respectively, C. curvus and C. destructor, described 
in the Trans, of the Royal Dublin Society (Vol. I., Ser. II., p. 376, 
pi. XLIX., figs. 14, 15). The former consists of three curved 
pointed denticles attached to a somewhat slender base, the posterior 
portion of which is hidden in the matrix, and consequently it is 
impossible to say whether it possesses the expanded base character- 
istic of the genus or not. C. destructor is similarly composed of 
three conical denticles, thicker in proportion to their length than 
