268 BRACHIOPODA 



of peduncle 16 em.: North Carolina to Florida; in vertical burrows in 

 the sand between tide lines, the contractile peduncle extending straight 

 down and the opening of the shell just reaching the water. 



Family 2. CRANIIDAE. 



Sliell more or less quadrate or circular in shape and without a 

 peduncle, being attached by the ventral valve to a rock; dorsal valve 

 limpet-like; tentacular arms free and spiral; mantle extending to the 

 edges of the valve, its margin being plain : 1 genus. 



Crania Retzius. Shell smooth or radiately striated: 4 species. 



C. anomala (0. F, Miiller). Shell brownish in color, 18 mm. long 

 and 22 mm. broad: Florida Keys and the West Indies, in 100 fathoms. 



Order 2. TESTICARDINES. 



Shell calcareous, the 2 valves being joined by a hinge; mantles also 

 fused behind; ventral valve larger than the dorsal and with a beak at 

 the hinder end through which the peduncle passes; tentacular arms 

 supported by calcareous arms which proceed from the dorsal valve; anus 

 wanting: 3 families and about 80 species; about 2,200 fossil species. 



Key to the families of Testicardines here described : 



Oi Shell with a sharp, hook-like beak 1. RirYNCHONELLiDAE 



«2 Beak not hook-like, but prominent 2. Terebratulidae 



Family 1. RHYNCHONELLIDAE. 



Shell more or less triangular with a sharp, hook-like beak; calcareous 

 arms long and slender, curving towards each other; tentacular arms 

 long and spiral: 2 genera and 8 species. 



Rhynchonella Fischer. Shell with radiating ridges; dorsal valve 

 very convex, ventral valve more flattened: 6 species. 



R. psittacea (Gmelin). Shell brown or black, 26 mm. long and not 

 quite so wide: circumpolar, being found south to the Gulf of St. Law- 

 rence and to the Aleutian Islands, in shallow water. 



Family 2. TEREBRATULIDAE. 



Shell round or oval, the lower valve with a prominent perforated 

 beak and 2 curved hinge teeth, dorsal valve w4th a hinge process and a 

 slender calcareous loop: about 10 genera and 68 species. 



Key to the genera of Terehratididae here described : 



fli Calcareous loop short 1. Terebratulina 



Oo Calcareous loop long. 



6i Loop with its principal stem attached but once 2. Waldeheimia 



h. Principal stem attached twice 3. Terebratella 



63 Reflected part of loop attached at the tip 4. Laqueus 



