207 

 Genus SPIRIFER. Sowerbv. 



[ Ety. : iSpirti, spire; fero, to bear.] 



(1815: Mineral Conchology, Vol. II., p. 42. 1898: Pal. N. Y., Vol. VIII., 



Pt. II., p. 1.) 



Shell variously shai)e(l, eoniinonly very iiincli wider than 

 long, radially }jlicated or striated, crossed by concentric 

 growth lines, which in some forms are lamellose or even 

 marked by spines. Hinge line generally long and straight. 

 Pedicle valve usually with moderately high area, with an 

 open delthyrium, the margins of which are prolonged into 

 stout simple teeth, supported by dental lamell.'e. Area of 

 the brachial vahe lower. A calcareous biachidium in the 

 form of a double spii-e, whose apices are directed towards 

 the cardinal angles, nearh' hlls the cavity of the shell. 



Spirifer mucronatus. (Conrad.) (Fig. llJr.) (Pal. 

 N. Y., Vol. IV., p. 216, PL XXXIV.) 



Distinguishing- Cluiracters. — Medium size; low^ cardinal 

 areas; much extended, often miicronate, hinge line, giving a 



Fig. 114. Spirifer luncnniiitiis. Dorsal (brachial) and ventral (pedicle) views of a 

 medium-sized specimen : dorsal and lateral views of different individuals (from Hall). 



width of from two to four times the height of the shell; 

 well-marked sinus in the pedicle valve, and fold in the bi*a- 

 chial valve, wdiicli is often flattened or gro o ved ; radiating pli- 

 cations, the outer ones of which do not reach the beak, and 

 lamellose lines of growth, often thickly crowded near the 

 front; short dental plates, and striated muscular areas. 



