No. 1.] MORPHOLOGY OF CLADOSELACHE. 97 
He finds in them, if anything, an argument against the lateral 
fold doctrine. He regards Cladoselache as ‘a typical selachian 
possessing all the essential peculiarities of its later relations.”’ 
That the fins were not, according to his interpretation, of dermal 
fold character is fatal evidence against the atavistic value of 
the early lateral folds of Torpedo.!8 ‘From the structure of 
its (Cladoselache) pectoral we shall find no possible ground 
for deriving the paired limbs from lateral folds,” but at the 
same time he admits that there is no ground for asserting 
the presence of the ‘“archipterygium” of Gegenbaur, and 
notes that it is of the plan of structure which Fritsch has 
shown as the stem-form for the paired fins of Xenacanthids, 
a group whose specialized archipterygium is evolved from its 
conditions of living. Cladoselache, he concludes, shows in 
the structure of pectoral nothing more than would be seen in 
an immature fin condition of modern sharks. The rays of the 
ventral joined to basal cartilages are adduced as an additional 
ground for the ungeneralized nature of the paired fins. 
At the present time the writer would regard the results of 
Jaekel as hardly to be warranted. Aside from the general 
primitive characters of the vadza/s, as pointed out by Smith 
Woodward, we now are able to determine from the basalia of 
the pectoral direct homologies with those of the ventral in 
the Permian forms,—vwe find indicated in the ventrals not 
Y 
the ‘“Flossenstrahlen” and “Knorpelspange”’ that Jaekel 
uses as an argument for its modern type of structure, but 
primitive, unjointed radialia and basalia that are as yet 
altogether unfused. In this remarkable basal condition the 
fin would at once seem more primitive than that of the 
cartilaginous ganoids,— which Wiedersheim states is below 
that of selachians, excluding Xenacanthids: the latter, he 
states, present the most generalized characters because they 
were lacking in hip girdle, show the fused basalia, and present 
as many as twenty radials. 
Cladoselache now becomes of interest, appearing to fore- 
shadow even these primitive characters. In its ventral it 
possesses 22-23 radials, as many as nine unfused _ basals, 
arranged in a way suggestive of lateral fold, with no axis 
