ORDER IV 



TELOTREMATA 



335 



This family is divided into the following sub-families Suessiinae, Uncitinae, and 

 Trigonotretinae. 



Ci/rtina, Davidson (Fig. 573). Cyrtia-\ike 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 

 Ct/rflnae. Alpine Trias. 



Eittnerula, Hall and Clarke. Like Thecocyrtella, but with the abbreviated 



FIG. 5 



A, Cyrtina heteroclyta, Defr. sp. Devonian ; Eitel. Vi- -B, Shell 

 with dorsal valve mostly removed, showing spiralia, / a (after David- 

 son). C, Cyrtina carbonaria, M'Coy. Carboniferous Limestone; 

 Kendal, Ireland, 1/1- Interior of ventral valve. The pseudodeltidium 

 is removed to show the dental plates and median septum. 



FIG. 574. 



Spiriferina restrain, Sow. 

 Middle Lias ; Ilminster. 1/1 

 Davidson). 



sp. 

 (after 



dental plates uniting with the very high median septum, forming a transverse 

 platform beneath the united deltidial plates. Alpine Trias. 



Spiriferina, d'Orb. (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 ; Europe. 



Untiles, Def ranee (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 

 Fischer de Waldheim 



FIG. 575. 



(Trigonotreta, Koenig ; ChoristUes, 



Brachythyris and Fusella, M'Coy; Uncites( , hus schi 



HysterolithuS, Quenstedt), (Fig. 576). Shell radially Devonian'''; Beuzberg, near 



plicated or striated, crossed by concentric growth-lines, c 

 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. 



