80 BEACHIOPODA. 



spirally coiled, fringed arms, which are supported 

 by a calcareous frame-work. 



Attached by the lower valve . Craniadce. 

 Attached by a footstalk: 



Vascular impressions branched; 

 arms supported by two minute 



plates Rhynchonelladte. 



No vascular impressions; arms 

 supported by a shelly loop . . . Terebratidadce. 



FAMILY I. CRANIAD^E. 



Shell roundish, hingeless, attached by the whole 

 breadth of the ventral valve ; dorsal valve limpet- 

 shaped ; interior of each valve with a broad granu- 

 lated border ; vascular impressions like the teeth 

 of a comb. Animal with free spiral arms, sup- 

 ported by a nose-like prominence in the middle of 

 the lower valve ; mantle plain. 



Crania (Retzius) . Point of dorsal valve nearly 

 central ; arms thick, fringed, arranged in a hori- 

 zontal coil of two or three turns. 



0. anomala. Fig. 120 ; mag. 



120 



FAMILY II. KHYNCHONELLAD^E. 



Shell somewhat three-sided, attached by a foot- 

 stalk ; ventral valve beaked ; valves convex, arti- 

 culated; hinge-line curved; vascular impressions 



