OF CONCHOLOGY. 159 



35. Planorbis declivis, Tate. 



Sliell orbicular, depressed, light horn colored, somewhat 

 shining, strongly and regularly wrinkled across ; tvlwrls four to 

 five, rounded, suture deep, the last two whorls flat above and be- 

 low, concealing the others; the spire and umbilicus deeply and 

 abruptly impressed ; last whorl suddenly deflected at the aper- 

 ture, which is horizontal and nearly circular ; peristome united 

 all round ; outer lip slightly reflected. 



Dimensions of adult shell : greater diameter '25 inch ; height 

 •075 inch. 



Marshy pools San Augustin near Acoyapa, living in company 

 with Planorhis kermatoides and Velletia excentrica. 



36. Planorbis Fieldii, Tryon. 



Distinguished from P. ffavanensis, Pfr., by being more de- 

 pressed, and in the white opacity of the under side of the shell. 

 Diam. -35 inch; height -1 inch. 



Pools bv margin of Lake Nicaragua at Grenada. Panama 

 (Field). 



37. Cyclotus translucidus, Sow. 



In the Chontales forest, where it is not uncommon, ascending 

 the Peiia Blanca to an elevation of nearly 3000 feet; it is 

 sparsely distributed in the savanna region. 



38. C. 



San Nicolas. 



39. Helicina denticulata, Pfr. 



The operculum is solid, purplish-brown, granulated. Ascend- 

 ing trees, Chontales forest, where it is rare ; it is known in 

 Honduras. 



40. Helicina rostrata, Morelet. 



Spi. — IT. Salvini, Tristram. 

 In the savanna region, San Diego ; it is a Guatemalan shell. 



41. Helicina turbinata, Wiegm. 



Forest, Toro Rapids ; hitherto only known from Mexico. 

 [Helicina semistriata, Sow. 



In the woods and cocoanut groves about Boca del Toro.] 



42. SPHiERiUM meridionals. Prime. 



Marshy pool near Javali, Chontales. Panama (Prime). 



