﻿174 I.AMPSII.IS 



dark rcddisli-hrown or Iilackish. becoming- olivc-colorcd on the 

 umbonal region : k-ft valve with two strong^, siibtriang-ular 

 pseudocardinals. wliicli the rouj:^h above, and two somewhat 

 remote laterals, the upper smaller ; rij>"ht valve with three 

 pseudocardinals. the central one laroi'e and trianj:jular, the 

 other two faint ; beak cavities moderate, with a row of dorsal 

 scars under the hin^-e ; anterior cicatrices well impressed ; pos- 

 terior cicatrices larjre. distinct ; nacre dark, lurid purple, with 

 a coppery iridescence behind, thicker in front. The only spec- 

 imen I have seen, the type, is probaibly a male and is very slig'ht- 

 ly rhomboid, bein^- feebly and widely biant^ulate behind near 

 the base ; basal line rounded. 



Length 90, heig^ht 60, diam. 40 mm. 



Rio Cosamaloapam. Chacotianiiuis : Tecomate River, Mex- 

 ico. 

 Ihiio tccomatensis Lea. Pr. Am. Phil. Soc. TL 1841. p. 30; 



Tr. Am. Phil. Soc. VIIL 1842. p. 234, pi. xxi, fig. 48; Obs.. 



TIL 1842. p. y2, pi. XXI, fig. 48. — Chenu, 111. Conch.. 1858. 



pi. xxxr, figs. 6. 6a, 6h. — Fischer and Crosse, Miss. Sci.. 



Pt. 7, TL 1894, p. 589. pi. Lxv, fig. 6; Lxvi, figs. 4. 4a. 

 Margaron fUnio) tccomaicnsis Lea, Syn., 1852, p. 2"/: 1870, 



p. 50. 

 LampsUis tecomatcnsis Simpson, Syn.. ic)oo, p. 571. 



This is not so rhomboid a shell as /,. bcdandierii, nor sa 

 much inflated ; its beaks are lower, and it has a darker epi- 

 dermis and nacre. Tt is shorter, more inflated, rather solider 

 than tampicoensis. and has a darker nacre. 



Lami'Sti.is livid.\ Simpson. 



Shell elongate, somewhat obovate. rather thin ; anterior end 

 compressed, ridge striated ; posterior end subtruncated above, 

 concentricallv finely ridged ; beaks quite full and high, placed 

 in front of the middle: epidermis smooth, livid olive, much 

 lighter on the beaks. The specimen figured in the Concholo- 

 gia is probably a female and has a slight, elongated, rounded 

 swelling along the ])osterior base : it is faintly biangulate be- 



