ORDERIV TELOTREMATA 335 
This family is divided into the following sub-families—Suwessiinae, Uncitinae, and 
Trigonotretinae. 
Cyrtina, Davidson (Fig. 573). Cyrtia-like shells, with the dental lamellae 
converging and united with the median septum. Loop V-shaped, complete. 
Silurian to Lower Carboniferous. Distribution general. 
Thecocyrtella, Bittner. Very small, ventrally cemented, smooth-shelled 
Cyrtinae. Alpine Trias. 
Bittnerula, Hall and Clarke. Like Thecocyrtella, but with the abbreviated 

Fic. 573 
A, Cyrtinw heteroclyta, Defr. sp. Devonian; Hitel. 1/4. 5, Shell 
with dorsal valve mostly removed, showing spiralia, 3/2 (after Dayid- Fic. 574. 
son). C, Cyrtina carbonaria, M‘Coy. Carboniferous Limestone ; Spiriferina rostrata, Sow. — sp. 
Kendal, Ireland. 1/;. Interior of ventral valve. The pseudodeltidium Middle Lias; Ilminster. © 1/; (after 
is removed to show the dental plates and inedian septum. Davidson). 
dental plates uniting with the very high median septum, forming a transverse 
platform beneath the united deltidial plates. Alpine Trias. 
Spiriferina, VOrb. (Fig. 574). Like Spirifer, but with the shell substance 
punctate, and a prominent ventral median septum. Loop 
simple, complete. Carboniferous to Jura. 
Suessia, Deslongchamps. Similar to Spiriferina, but 
the dental plates not extending to the bottom of the valve. 
Jugum with a median process. Jura; Kurope. 
Uncites, Defrance (Fig. 575). Shells rostrate, striate, 
with the ventral beak long, frequently distorted and 
arched. No cardinal area. Deltidial plates united, 
forming a concave plate. Pouch-like plates just within 
the margins of the dorsal valve. Devonian; Germany. 
_ Uncinella, Waagen. Carboniferous ; India. 

Spirifer, Sowerby (Trigonotreta, Koenig; Choristites, cages 
Fischer de Waldheim ; Brachythyris and Fusella, M‘Coy Fate aia nity 
Hysterolithus, Quenstedt), (Fig. 576). Shell radially Devonian; Benzberg, near 
plicated or striated, crossed by concentric growth-lines, °°" 
lamellae, simple, or compound spines. Hinge-line generally long and straight. 
Ventral valve usually with moderately high cardinal area, and stout simple 
teeth supported by short dental lamellae. Delthyrium open. Spirals directed 
towards the cardinal angles of the valves. Jugum at maturity represented 
by two short spur-like processes, which are not in contact with each other. 
Generally distributed and extraordinarily abundant in the Silurian, Devonian, 
and Carboniferous. 
