04 



PALEONTOLOGY OF NEW YORK. 



umhonuia, possesses a peculiar loop connecting the spirals, and has, therefore, 

 upon this character based a distinct genus. The situation of this organ, the 



Fio. 46. Fig. 47. 



The primary lamellie and loop of Hindella umbondta, Billings, (c.) 



loop, is very far forward, and its inclination to the primary lamellae is extremely 

 oblique, the lateral processes or branches being directed backward in a low up- 

 ward curve, uniting to form a short, straight, undivided stem. The posterior 

 extremity of the entire process rarely extends back of the middle of the first 

 lamellae and does not rise to the center of the bases of the spirals. 



The form of this loop is somewhat similar to that occurring in the genera, 

 Whitfieldella, Hyattella, Nucleospira, etc., but its anterior position on the 

 primary lamellae and its very depressed form are without parallel among these 

 brachiopods with everted spirals. 



Congeneric with Hindella umbonata is Billings' Athyris Prinstana, from the same 

 locality ; a shorter and more rotund form than H. umbonala, but probably no 

 more than a variation of that species. 



Q ISS 



Fig. 48. Fig. 49. FiG. 60. Fig. 51. 



Consecutive transverse sections of tlie umbonal region of Hindella umbonata, Billings. 

 Fig. 48. Section just below apex of peiliole-valve, showing the grooved pedicle-passage. 

 Fig. 49. Section at ape.x of brachial valve, showing the dental lamellae. 



Fig. 60. A deeper section, e-thibiting the teeth, and the remnants of the dental lamella; bounding the muscular area. 

 Fig. 61. Section showing the lateral elements of the hinge-plate. (c.) 



Some additional characters of these shells may be added : 

 The outline is subcircular or elongate-ovate ; the valves convex ; the pedicle- 

 valve being gibbous in the umbonal region. The hinge-line is very short but 

 the cardinal slopes are frequently long and transverse, which, with the fulness of 



