146 PERMIAN FOSSILS. 



Genus Epithyris, Phillips/ 1844. 



Terebbatula, Auct. 



1"^ Sous-Sect., l'^^ Div. Bbachiop. (Ipartim), Eudes-J)eslongchamps, 1837. 



Diagnosis. — A longitudinally-oblong Terebratulidia ; furnished with prominent 

 dental plates, and a transversely semi-elliptical, moderately recurved loop. 



Type Terebratulites elonc/atus, Schlotheim. 



Professor Phillips, in his ' Palaeozoic Fossils,' proposed the name Epithyris as a 

 substitute for that of Terebratula ; and at the same time applied it to a generic group, 

 which he characterised as having " the beak truncate, perforate." The name has 

 hitherto been considered in the light of a synonym ; but I propose applying it to one 

 of the subdivisions of the old genus Terebratula, represented by the Permian species 

 above named, and distinguished from all its co-ordinates, hitherto noticed, by having 

 its rostral cavity furnished with prominent dental plates, and its apophysary system 

 somewhat resembling the half of a transversely bisected ellipsis. Waldheimia is 

 most intimately related to Epithyris ; but the difference will be at once evident by a 

 reference to the figures representing their respective internal structures (vide PI. VI, 

 fig. 45 ; PI. XX, fig. 1 1). In Waldheimia the loop is elliptical, deeply recurved, 

 and projecting about two thirds of the length of the shell ; but in Epithyris it is semi- 

 elliptical, moderately recurved, and projecting about one third of the length of the shell. 



The differences just noticed clearly indicate a distinction in the animal ; because, 

 from the short and slightly recurved character of the loop of Epithyris, it must be 

 concluded that the labial appendages have been either unusually short and attached 

 throughout their entire length, or long and free towards their base. But in either case 

 a difference is involved, of sufficient importance to constitute a generic distinction 

 between Epithyris and Waldheimia ; inasmuch as in the latter the labial appendages, 

 although long, are nevertheless attached throughout their entire length. In the view 

 taken, Epithyris also becomes related to Terebratula ; but the greater distance of the 

 cross piece of the loop from its crura, in the former, indicates that the visceral mass 

 has been more voluminous than it is in the latter. The difference in this respect is 

 still greater between Epithyris and Waldheimia, in consequence of the cross piece of 

 the latter being brought nearly in contact with the crura (vide PL XX, fig. 11). On 

 the whole, it would appear that the present genus, in its loop and labial appendages, 

 is intermediate between Terebratula and Waldheimia. 



Epithyris appears to have been the earliest created genus of Terebratulidce ; as 

 species occur in the Devonian rocks : remains are also present in deposits belonging 

 to later periods ; but none are known to me as occurring in more recent rocks than the 

 Jurassic. 



' Palaeozoic Fossils, p. 55. 



