222 



MANUAL OF THE MOLLUSCA, 



Fig. \30. Dorsal valve. Profile.* 



a, adductor ; c, crura ; I, loop ; j, cardinal process ; p, hinge-plate ; s, dorsal septum ; 

 V. s. ventral septum; t, dental sockets. 



? Stringocephalus, Defrance. 

 Etf/m. Strinx {stringos) an owl, cephale the head.f 

 S. Burtini, PI. XV. fig. 13. Tig. 130, 131. Devonian, Europe. 

 Shell punctate; sub-orbicular, with a prominent beak: ventral valve 

 with a longitudinal septum {v.s.) in the middle; hinge-area distinct ; foramen 

 large and angular in the young shell, gradually surrounded by the deltidium 

 and rendered small and oval in the adult; deltidium 

 composed of three elements; teeth prominent; dorsal 

 valve depressed, cardinal process {j) very prominent, some- 

 times touching the opposite valve, its extremity forked 

 to receive the ventral septum {v.s.); hinge-plate {p) sup- 

 porting a shelly loop, after the manner of Jrgiope. 



Fig. 131.t 



TAISIILY II. Spirtpekid^. 



Shell furnished internally with two calcarious spiral processes {apophyses) : 



directed outwards, towards the sides of the sheU, and destined for the support ! 



of the oral arms ; which must have been fixed immoveably; the spiral lamellae \ 



* The loop (which was discovered by Prof. King) has a distinct suture in the 

 middle ; the dotted lines proceeding from its inner edge are added from a drawing by 

 Mr. Suess, and represent what he regards as shelly processes for supporting a mem. 

 branous disk. They may be portions of spirals, -whose outer whirls are confluent. 



f Internal casts of Producta gigantea are called " owl-heads" by quarrj^men in the 

 North of England. [Sowerby). 



I Fig. 131. Young shell, magnified 4 diameters; A, hinge area; b, deltidium: 

 p, pseudo-deltidium. 



