PELECTPODA 



581 



2. STROPHITTTS* Rafmesque. Shell inflated, rounded, with a hard, 

 shining periostracum ; teeth rudimentary, consisting of an irregular ridge 

 in the left and 1 or 2 faint ridges in the right valves; male and female 

 shells alike; glochidia not parasitic: 8 species, all American. 



S. edentulus (Say) (Fig. 913). Shell ovate, hinder margin forms 

 an obtuse angle with dorsal margin ; umbo but little in front of the mid- 

 dle; interior, bluish-white; surface yellowish, with dark rays; lengtn 8 

 cm. ; height 4 cm. ; width 3 cm. : eastern and central states. 



3. ANODONTA Lamarck. Shell thin, oval or elongate, inflated; peri- 

 ostracum generally smooth and without rays; hinge without teeth, regu- 

 larly curved; cloacal siphon without papillae; male and female shells 

 alike: 55 species, 30 American, the animals living usually in muddy 

 streams and ponds, often buried in the mud. 



Key to the species of Anodonta here described: 



o x Shell large. 



&! Dorsal margin straight A. CATABACTA 



6 a Umbo with undulating wrinkles A. GBANDIS 



& 3 Shell with very thick margins A. IMPLICATA 



o, Shell small and bright green A. IMBECILIS 



A. cataracta Say (A. fluviatilis Gould) (Fig. 914, A). Shell oval, 

 large, crested behind, deep green in color, with obscure radial rays, 

 white within, with a lilac tint; hinge margin straight; 11 cm. long, 7 cm. 

 high, 37 mm. wide; shell 

 rounded in front and form- 

 ing an obtuse angle behind : 

 Atlantic slope, south to 

 North Carolina; common. 



A. grandis Say (Fig. 

 914, C). Shell elliptical, in- 

 flated, green or black in 

 color, with usually faint 

 radiating rays, 12 cm. long, 

 7 cm. high, and 5 cm. wide, 

 or larger; umbo marked with about 5 elevated undulating wrinkles: 

 central states; common. 



A. implicata Say (Fig. 914, B). Shell oval, thick and heavy, with a 

 rough, light yellowish-green outer, and a pink inner surface, 10 cm. long, 

 56 mm. high, and 35 mm. wide ; hinder end with a truncated point which 

 is joined with the umbo by a very pronounced edge :- Atlantic slope as 

 far south as Virginia ; valley of the St. Lawrence. 



* "Metamorphosis without Parasitism," etc., by G. Lefevre and W. C. Curtis, 

 Science, N. S., Vol. 33, p. 863. 



Fig. 914 



A, Anodonta cataracta (Gould) ; B, A. implicata; 

 C, A. grandis; D, A. imbecilis (Baker). 



