320 SPIRIFERID A. 
of the spiral cones in the type same as in Zygospira, the base of 
each spiral cone being oni ety inclined towards the bottom 
and sides of the ventral valve; there are about four coils in 
each spiral cone; the primary stems of the spirals are attached 
to the hinge-plate of the dorsal valve; and after extending 
parallel to each other for a short distance, they bend at right- 
angles abruptly towards the lateral portions of the beak, and 
form two large curves facing the lateral portions of the valve ; 
just before reaching their furthest extension in front they give 
off a semicircular band or loop, which is directed upwards 
towards the beak, and is exterior to the spiral cones on their 
dorsal side. 
Famity SPIRIFERID A. 
Shell furnished internally with two calcareous spiral processes 
(apophyses) directed outwards towards the sides of the shell, and 
destined for the support of the oral arms, which must have been 
fixed immovably ; the spiral lamellz are sometimes spinulose, 
indicating the existence of rigid cirri, especially on the front of 
the whorls ; valves articulated by teeth and sockets. 
SPIRIFER, Sowerby, 1815. 
Syn.—Trigonotreta, Kénig, 1825. Choristites, Fischer, 1825. 
Delthyris, Dalman, 1828. “Fusula, Reticularia, Brachythyris, 
M’Coy, 1844. 
Disir.—300 sp. Lower Silurian—Trias; Arctic America— 
Chili, Falkland Islands, Europe, China, Thibet, Australia, Tas- 
mania. In China these and other fossils are used as medicine. 
S. striatus, Mart. (cxxxvii, 5, 96). S. Wolcottt, Sowerby 
(Cxxxvii, 97). 
Shell transversely oval or elongated, trilobed, beaked, biconvex, 
with a dorsal ridge and ventral furrow ; hinge-line wide and 
straight ; area moderate, striated across ; foramen angular, open 
in the young, afterwar ds progressively closed : ventral valve with 
prominent hinge-teeth, and a central muscular scar, consisting of 
the single adductor flanked by two cardinal impressions ; dorsal 
valve with a small cardinal process, a divided hinge- plate, and 
two conical spires directed outwards and nearly filling the cavity 
of the shell; crura united by an oral loop. The shell and Spires 
are sometimes silicified in limestone, and may be developed by 
means of acid. In S. mosquensis the dental plates are prolonged 
nearly to the front of the ventral valve. 
SPIRIFERINA, d’Orbigny, 1847. (Mentzelia, Quenst., 1871.) 
Shell punctate, external surface spinulose; foramen covered by 
a pseudo-deltidium ; interior of ventral valve with a prominent 
septum, rising from the adductor scar. 29 sp. Carb.—Lower 
Oolites; Britain, France, Germany, South America. S. rostrata, 
Schloth. (exxxvii, 98-100). 
