POTAMIDES. 159 



P. Lamarckii, Valcnc. PI. 31, fig. 33. 



Fawn or light chocolate color, whorls shouldered, plicate, sloping 

 to a peripheral double angle, with a double line of small tubercles. 



Length, 1"35 in. 



Const of Cumana, Venezuela. 



Subgenus Tympanotonos, Klein., 1753, 

 P. FuscATUs, Linn. PI. 31, fig. 34. 



Solid, spinosely tuberculated in the middle of the whorls, with 

 spiral rows of granules above and below the suture, body whorl 

 with two rows of granules below the peripheral angle, base closely 

 spirally ridged ; epidermis thick, chocolate brown, aperture yellow- 

 ish white. Length, 2'3 in. 



Gambia, Gape Palmas, W. Africa. 

 P. viuricatus, Qj'ug., and P. cingulatus, Gmel., are synonyms. 



P. RADULA, Linn. PL 31, figs. 35, 36. 



Spirally ridged, and beaded by the crossing of longitudinal rib- 

 lets, whorls concavely channeled below a sutural row of beads, base 

 spirally ridged; epidermis dark chocolate color. Length, 1-75 in. 



W. Africa. 



Different as this appears from the preceding species, the speci- 

 mens before me almost prove a transition from one into the 

 other. P. terehella, Gmel., P. gramdahis, Brug., P. Jluviatilis, and 

 P. aculeatus, Gmel., P. Oivenii, Fer. (fig. 36), are synonyms. 



P. HOMOLOGUM, Baylc. PI. 31, fig. 37. 



Narrower, more cylindrical than the preceding species, sculpture 

 similar in pattern, but more minute; variegated chocolate and 

 white. Length, 1-75 in. 



W. Goast of Africa. 



This is P. multigranosus, Sowb., preoccupied by Deshayes for a 

 fossil species. 



P. FLUviATiLis, Potiez et Michaud. PL 31, figs. 38-40; PL 32, 



figs. 49, 51, 52. 



Whorls flattened, with deeply incised suture, each with three flat- 

 topped spiral ribs, tuberculated in longitudinal rows, tubercles 

 obsolete on the back of the body whorl except a sutural row, base 

 spirally ridged ; aperture in the adult expanded, angularly pro- 

 duced above, oblique, outer lip produced below ; yellowish white or 

 glaucous, narrowly banded with chocolate, sometimes white-banded 

 at the suture. Length, 2 in. 



