﻿192 I.AMl'SirjS 



Unio sciitulatiis MoKici.KT, Test. Noviss., I, 1849, P- 3^- — l^'iscn- 

 KR and Crosse, Miss, Sci., II, 1894, p. 561, pi. lix, fig. 5; 

 i.xvii, fig. 6. 

 Lainpsilis scntiilatns Simtson, Syn., 1900, p. 576. 



This species, L. planivalvis and L. pahidosa, are very closely 

 related and may be mere variations of one thing. This has 

 strong, nearly vertical, ribs on the posterior half of the shell 

 and the male shells are more round on the base than those of 

 either of the other species. L. paiiidosa has a higher wing than 

 either of the other forms and is shorter than plank-ak-is. 



Lamtsilis paIvUDOSa (Morelet). 



Shell winged, inequilateral, oval-trapezoidal, compressed, 

 thin, with a greenish-olive epidermis ; surface covered with 

 concentric growth lines, slightly radiately sculptured on the 

 umbonal region ; beaks low but sharp, not inflated, with deli- 

 cate, doubly-looped sculpture ; posterior ridge well developed 

 and angled ; anterior end rounded, angled at the dorsal line ; 

 posterior wing considerably developed and angled behind ; the 

 shell is decidedly and obliquely truncated posteriorly ; post-basal 

 part sub-biangulate ; left valve with two pseudocardinals, the 

 hinder rudimentary, and two lamellar laterals ; right valve 

 with two pseudocardinals, the upper the smaller, and one 

 lateral ; beak cavities shallow ; nacre pale violet-rose ; anterior 

 muscle scars superficial ; posterior scars indistinct. 



The specimen described is probably a male ; its basal line is 

 nearly straight and it is considerably rhomboid. 

 Length 57, height 31, diam. 15 mm. 

 Yucatan. 

 Unio pallid osus Morelet, Test. Noviss., I, 1849, P- 2P- — Fisch- 

 er and Crosse, Miss. Sci., II, 1894, p. 559, pi. ux, fig. 3. 

 Lainpsilis paludosus Simpson, Syn., 1900, p. 576. 



A fine, compressed species with a small, angular wing in 

 front and a larger one behind. It is nearly smooth, the pos- 

 terior slope, however, sometimes has a few plications. It is 

 more inflated and shorter than planivalvis and does not have 

 such high wings as delphinulus. 



