36 University of Michigan 



The inside of the aperture of these greenish-yellow shells 

 is pearlv. hut without dark iridescence. The peristome is often 

 noticeably thickened, and even flares outward, with several, 

 heavv varices, so as to be almost campanulate. Its l)asal lip is 

 quire even, and the ai)erture is almost circular. The exterior 

 surface of the operculum is quite markedly concave, and the 

 internal boss is prominent. The specimens have lietween 4^/2 

 and 5 whorls, and the umbilicus is a little over ^4 the major 

 diameter. 



A set of specimens of Potcria (jninadciisis nigata (r7Ui)pv). 

 from Cariaquito. Venezuela (A. N. S. P. no. 104625; S. 

 Brown. 191 1 ) show that this Trinidad shell also reaches the 

 mainland. Measurements of seven males and seven females 

 are summarized in the accompanying table (cf. figs. v-P. O). 



Dimensions in Group of P. stramiiiea 



Altitude Maj.Diam. 



P.strammca i5-~ 142(22.3) Figure. Thesaurus. 



Means; 30 specimens 12.5 147(18.3) H. I, c. 2. 3. 4: San Esteban. 



Extremes; ditto 9.7-15-9 131-158 (i4-7-22.6) Figs. v-K, O. 



P.granadcmisrngata io.2(sic) (i7-8) Guppy, (1864). 



A. N. S. P. 104625. 



Means: 7 females 8.6 146 (12.3) Cariaquito, ^'enczuela. 



Extremes: ditto 8.3-9-2 138-156 (ii.9-i3-4) Fig. v-P. 



Means: 7 males 7-8 142 (ii-O 



Extremes: ditto 7-3-8-2 132-148 (10.2-11.4) Fig. v-Q. 



P. glaucostoma 12.8 142 (11.4) Figure. Reeve. Conch. Icon. 



P. g. ait I all 



Means: 4 specimens i5-5 146(22.7) H, II, he. 20: Palma Sola. 



Extremes: ditto 14.1-16.8142-154(20.8-24.6) Fig. v-M. 



Means: 6 specimens 14.6 154 (22.6) 1 1. II. he. 28; Quchrada Seca. 



Extremes: ditto 13.3-16.2 149-161 (21.3-24.8) Figs. v-K, L. 



The following, artificial key, to the nieml)ers of the group 

 of /'. straminca, is i)resented. The remarks, which precede the 

 kev to the first grouj), also apply here. The first species is in- 

 cluded with considerable doubt. 



