Figure 8. — Egg case of a cat shark collected from 100 

 fathoms off the coast of North Carolina, showing an em- 

 bryo with the two series of enlarged denticles that 

 characterize the young in some species of scyliorhinid 

 sharks. Presumably this is an embryo of Scyliorhinus 

 retifer. The somewhat opaque white banding in the 

 shell has not been reported previously and may not 

 always be evident in egg cases of the species. 



males of that species not only have teeth twice 

 as long as the teeth of females of comparable size 

 but the teeth of the males are also quite different 

 in shape from those of the females, with lateral 

 cusps entirely absent on the teeth of the central 

 part of the jaws. A few teeth with lateral den- 

 ticles or cusps are present among the last few rows 

 toward the angles of the jaws. 



This degree of dimorphism illustrated by the ac- 

 companying diagram (fig. 10) does not occur in 

 the other species of Apristurus that are represent- 

 ed by sufficient material to check. The teeth of 

 males of the Pacific species, Apristurus brunneus, 

 are somewhat larger than the teeth of females of 

 comparable size, but there is no important differ- 

 ence in tooth shape, No significant dimorphism 

 is present in A. pr&fundorum, A. indicus, or A. 

 laurussoni. 



It is suggested that (he modification in teeth 

 would function effectively to hold the female, per- 

 haps by the pectoral fin, during copulation. 



With reference to Halaehirus from Patagonia, 

 Yaillaiu (1891) states that: one finds greal vari- 



1 mm 



Figure 9. — Camera lucida outlines of teeth from upi>er and 

 lower jaws, shark's right side, fifth lateral row count- 

 ing from the symphysis: A, Soyliorhinus hespervus, a 

 272-mm. female ; B, Galcus arac. a 365-mm. male ; C, 

 Schroederichthus maculatus, a 220-mm. male; and D, 

 Apristurus indicus, a 430-mm. female. 



ation in the teeth of the lower jaw with differences 

 following size and perhaps sex. Also in a table 

 of differences between Scyllium biviu/m and S. 

 chMense {ScyMium= Halaehirus), Vaillant notes 

 that the lower jaw teeth of biviiim are not very 

 small and are either without lateral cusps or with 

 lateral cusps not very distinct, whereas the teeth 

 of the lower jaw in chilense are very small and 

 have no lateral points. In spite of complications 

 of nomenclature and contradictions in the litera- 

 ture, it is obvious that South American Halaehirus 

 exhibit a transition in tooth form. A more 

 thorough study is necessary to determine whether 



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U.S. FISH AND WILDLIFE SERVICE 



