BRACHIOPODA. 



91 



crura not only at their apices but for a short dis- 

 tance along their inner faces, not making the 

 nooses peculiar to Athyris proper ; they are broad 

 and blade-like, narrowing beyond the insertion of 

 the loop ; the loop is situated posteriorly ; the 

 accessory lamellae are narrow near their origin, 

 broaden and then taper again, having the shape of 

 a sickle. The spiral ribbon, from the figures given 

 by Davidson and King, appears to be pectinated on 

 all its outer edges, but it has not been shown that 

 the anterior extremity of the loop is similarly 

 ornamented. 



FIG. 64. 

 The fimbriated spirals ot Athyris pectin- 

 t/"«-<», Sowerby. (DAVIDSON.) 



These features are of sufficient significance to distinguish this group of 

 species from the typical division of the genus. It must be granted, that as the 

 really essential differences are in the structure of the spirals and loop, it 

 will be impossible to make a final arrangement of these species until their 

 internal structure has been fully elucidated. Temporarily, however, the char- 

 acter of the external ornament may be relied upon, inasmuch as we know 

 the internal arrangements with which it is associated in the type-species, 

 Cliothyris pedinifera. 



This subgenus is equivalent to Waagen's section Ornat.e, typified by the 

 Athyris Roysii, Leveille,* under which he includes, besides A. Roysii and A. 

 pedinifera, five new species {A. subexpansa, A. capillata, A. semiconcava, A. acuto- 

 marginalis, A. globulina), all from the upper and lower divisions of the Productus 

 limestone of the Salt-Range of India. In American faunas Cliothyris is rep- 

 resented by the species usually identified as A. Roysii, in the Waverly and 

 Keokuk divisions of the lower Carboniferous, A. hirsuta. Hall (= A. americana, 

 Swallow), from the St. Louis and Chester limestones, and A. sublamellosa, Hall, 

 from the Burlington limestone. 



* Pi-oductus limestone Fossils, p. 473. 1883. 



