142 PALAEONTOLOGY OF NEW YORK. . 



shell allied to Leptocalia flabellites in the structure of its cardinal process and 

 articulating apparatus, having, however, a highly convex brachial valve with a 

 median septum extending one-half its length, two short, abruptly ending 

 plications on the low median fold, upturned anterior margins, and explanate 

 cardinal extremities. As far as the structure of its type species, Anabaia Paraia, 

 Clarke, is known, it appears to be the precursor of the Devonian shells referred 

 to Anoplotheca and Leptocoelia. 



Genus NUCLEOSPIRA, Hall. 1859. 



PLATE XLVIII. 



1843. Atrypa, Hall. Geology of N. Y.; Rept. Fourth Dist., p. 200, fig. 3. 



1852. Ort'his, Hall. Palaeontology of N. Y., vol. ii, p. 250, pi. Hi, tig. 1. 



1857. Spirifer, Hall. Tenth Rept. N Y. State Cab. Nat. Hist., p. hi. 



1859. Nudeospira, Hall. Twelfth Rept. N. Y. State Cab. Nat. Hist., pj). 24-26. 



1859. Nudeospira, Hall. Palaeontology of N. Y,, vol. iii, pj). 219-223, pi. xiv, fig. 1 ; ]il. xxviii, b, 



figs. 2-19. 



1860. Nudeospira, White. Jour. Boston Soc. Nat. Hist., vol. viii, p. 227. 

 1863. Nudeospira, Hall. Transactions of the Albany Institute, vol. iv, p. 226. 



1867. Nudeospira, Hall. Palaeontology of N. Y., vol. iv, pp. 278, 279, pi xlv, tigs. 33-57. 



1879. Nudeospira, Hall. Twenty-eighth Rept. N. Y. State Mus. Nat. Hist., p. 160, pi. xxv, tigs. 22-28. 



1882. Nudeospira, Hall. Eleventh Rejit. State Geologist of Indiana, p. 301, pi. xxv, tigs. 22-28. 



1882. Nudeospira, Whitfield. Annals N. Y. Acad. Sciences, vol. ii, p. 194. 



1884. Nudeospira, Walcott. Monogr. U. S. Geol. Survey, vol. viii, p. 147. 



1889. Nudeospira, Nbttblroth. Kentucky Fossil Shells, pp 103, 104, pi. xxxii, figs. 1-4 ; pi. xxxiii, 

 figs. 7-9. 



Diagnosis. Shells usually small, subcircular in outline. Valves subequally 

 convex, often gibbous or ventricose. Hinge-line very short, cardinal ex- 

 tremities rounded. On the pedicle-valve the cardinal area is low and 

 obscured by the incurvature of the beak. Only in very young specimens 

 is the deltidium exposed, and it then consists of two plates attached to 

 the lateral margins of the delthyrium; in mature individuals these plates 

 are coalesced and incurved, the median suture is lost and the foramen 

 covered ; the appearance of the deltidium is that of a triangular concave plate, 

 limited by rather sharp dental ridges and covering the delthyrium for about half 

 its length. The teeth are prominent, approximate, recurved at their tips, sup- 

 ported by thickened bases but not by lamellte. Dental sockets very narrow. 

 The muscular area is flabellate and extends for nearly one-half the length of 



