222 



MANUAL OP THE MOLLUSCA. 



I 



Fig. 130. Dorsal valve. Profile* 



a, adductor; c, crura; /, loop; .;", cardinal process; p, hinge-plate; s, dorsal septum ; 

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



? STRINGOCEPHALUS, Defiance. 

 Etym. Strinx (stringos) an owl, cephale the head.f 

 S. Burtini, PI. XV. fig. 13. Fig. 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 (/) 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 Argiope. 



Fig. 131.1 



FAMILY II. SPIRIFERIDJS. 



Shell furnished internally with two calcarious 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 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. 



t Internal casts of Producta gigantea are called " owl-heads" by quarrymen in the 

 North of England. (Sowerby). 



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

 p, pseudo-deltidium. 



