C. R. Eastman — Tamiobatis vetustus. 89 



Palaeozoic Tectospondyli were known, we would not have so 

 slender a basis for comparison ; but as it is, we are singularly 

 limited. True, evidence is not wanting to show that cartilagi- 

 nous fishes with a much-depressed body, probably like that of 

 existing rays, were plentiful in the Palaeozoic. The teeth 

 known as Psammodonts, for instance, belonged undoubtedly to 

 ray-like Elasmobranchs ; but no trace of their skeletons has yet 

 been discovered. We should not expect them, however, to 

 differ very widely from Mesozoic or even recent raj 7 s ; their 

 bodies were more generalized, of course, partaking of the 

 nature of both shark and skate; but the idea that the distinc- 

 tion between a shark-skull and a skate-skull was not brought 

 about until the skates began to specialize markedly along par- 

 ticular lines (i. e., since the Jurassic), cannot be entertained. 

 In fact, it does not strike us as surprising that a Palaeozoic 

 skull, such as has just been described, should present the 

 resemblance it does to the crania of existing skates. The speci- 

 men at hand merely proves what has long since been postu- 

 lated, — that there were Palaeozoic forerunners which were very 

 like Mesozoic rays; and it is to be observed that a number of 

 Mesozoic genera survive at the present day. So far material 

 has been lacking to demonstrate the conservatism as well as 

 remote antiquity of the ray tribe ; but as the palaeontological 

 record becomes more fully revealed, we shall probably find 

 that this group diverged very early from the parent stem, and 

 did not become highly modified until comparatively late in 

 time. 



Of existing families, the Phinobatids and Myliobatids are 

 generally believed to represent the most nearly ancestral form 

 of ray, and it is natural to look to them first of all for fur- 

 nishing points of resemblance to the present specimen. But 

 as we have here nothing more than the skull to base com- 

 parisons upon, and this is not sufficiently characteristic, it is 

 manifestly impossible to single out any one genus or even 

 family and declare that the fragment approaches it more closely 

 than other living types. We can only affirm that the fossil 

 skull indicates a very generalized condition; it presents some 

 features that are shark-like, and differs notably from the skulls 

 of existing rays. Doubtless the fin-structures and body-parts 

 were also generalized ; the indications are that the skeleton of 

 the pectoral fins was not continued forward to the snout; and 

 the dentition was probably weak. In all these respects there is 

 an agreement with Rhinobatas, obviously because it, too, pos- 

 sesses a generalized organization ; but there are differences in 

 detail which prevent it from being included under the same 

 family. With still less propriety can it be assigned to any other 

 recognized family : but as the group to which it belongs is imper- 



