BnACHIOrODA. 



1 1 1 ^ . > 



edges rolled together and united, forming a large permanently 

 open tube for the brachial currents. The large spines are most 

 usually situated on the ears of the ventral valve, and may havo 

 served to moor the shell ; being tubular they were permanently 

 susceptible of growth and repair. Although edentulous, the 

 dorsal valve must have turned on its long hinge-line with as 

 much precision as in those genera which are regularly articulated 

 by teeth. 



Fossil, 81 sj)ecies. Devonian — Permian. North and South 

 America, Europe, Spitzbergen, Thibet, Australia. 



Exterior. 



Fig. 190. 



Interior. 



Fio-. 



Suh-yemis. Auhst€(/es,'KclmeTsen. A. "Wangenheimii, Yern., 

 190. Permian, Eusssia; Carb. Shell like Producta; 



ventral valve with a large flat triangular hinge-area (h), with a 

 narrow convex pseudo-deltidium [d) in the centre ; beak a littlo 

 distorted, as if attached when young ; dorsal valve slightly 

 convex near the umbo ; interior as in Productus {longi-spinus). 



Strophalosia, Xing. 



Example, S. Cancrini, De Yern., Fig. 

 191. 



Synomjm, Orthothi-ix, Geinitz. 



Shell attached by the umbo of the 

 ventral valve ; sub-quadrate ; covered 

 with long slender spines ; valves arti- 

 culated, dorsal moderately concave, 

 7entral convex, each with a small area ; 

 fissure covered; vascular impressions 

 conjoined, reniform. 



Fossil, 8 species. Devonian — Carb. 

 Europe, Himalaya (Gerard). 



Tig. 193 5. Cr.ncrin. 



