SPIRIFERID^. 323 



Charionella, Billings, 1861. 



S;/»._Cryptonella, Hall, 1861. 



IJistr. — 15 sp. Devonian ; America, Spain. C. scitula, Hall. 



Shell resembling Athyris, but more elongate-ovate or approach- 

 ing to Terebratula in form. Internal spires as in Athyris and 

 Merista, but the dorsal hinge-plate is either obsolete along the 

 middle, or anchylosed to the bottom of the valve. Foramen 

 terminal, bounded on the lower side b}^ one or two deltidial 

 pieces, or by a portion of the shell. The mesial septum in the 

 dorsal valve is either absent or rudimentarj^ 



NucLEOSPiRA, Hall, 1859. 



Etym. — Nucleus^ and spira. 



Bistr. — 1 sp. Silurian, Devonian ; United States, England. 

 N. ventricosa, Hall (cxxxviii, 16-18). 



Shell punctate ; spheroidal ; beaked ; hinge-line shorter than 

 the width of the shell ; cardinal extremities rounded. Internal 

 spires as in Spirifera. Yentral valve with a flattened space or 

 false area beneath the beak, on each side of which, at the base, 

 is a strong tooth ; a narrow medio-longitndinal septum extends 

 from the beak to the base. Dorsal valve furnished with a strong 

 spatnlate cardinal process, which, rising vertically from the 

 cardinal margin, is closely grasped at its base by the cardinal 

 teeth of the other valve; and thence bending abruptly upwards, 

 and expanding, is projected into the cavity of the opposite beak, 

 lying close upon the under side of the false area. Cardinal 

 process grooved to allow of the passage of the peduncle, for the 

 protrusion of which a minute foramen is sometimes observed in 

 the beak. The crural processes originate at the base of the 

 cardinal process. A medio-longitudinal septum as in the ventral 

 valve. 



Surface of shell apparently smooth, under a lens punctate ; 

 when perfect, covered with minute hair-like spines. 



The larger species of this genus present some analogy in 

 external appearance with Spiiigera, and the presence of internal 

 spires increases the similarity. The cardinal teeth resemble 

 those of Spirigera and Merista. In form, and in the punctated 

 test, it simulates Magas ; while the elongate cardinal process of 

 the dorsal valve resembles that structure in Thecidium. 



Merista, Suess, 1851. 



Syn. — Camarinm, Hall, 1859. 



Bistr. — Silurian — Devonian ; Europe, JST. Am. M. herculea, 

 Desl. (cxxxviii, 19). 



Shell impunctate, dental plates and dorsal septum supported 

 by arched plates (^" shoe-lifter" processes, of King) which readily 



