518 



MEMOIRS OF THE CARNEGIE MUSEUM. 



hurrotighiamts in shape, diinensions, and color. Others differ more or less, chiefly 

 in having the posterior point of the shell less elevated above the base-line. Thus 

 they approach other species described by Lea as piger (1860) and ampullaceus 

 (1869), both from the Uruguay River (See also mnqmllaceus, Haas, 1916, i)p. 11, 

 47). My material is not sufficient to work out the synonymy. 



Measurements. * 



The two specimens measured by Simpson do not include the type. They are 

 more compressed than any others. 



Anatomy. — The soft parts of a male and a female are at hand. 



Color of soft parts whitisli, distal part of foot grayish. 



Anal opening slit-like, closed above, short, shorter than the branchial opening, 

 separated from the latter by a connection of the mantle-margins. Branchial 

 opening short, its inner edge with small, but distinct papillse. Palpi subtriangular, 

 moderately large, lower margins convex, posterior margins united at base for a 

 short distance. 



Gills of the usual shape; the inner the wider, chiefly in front, its anterior end 

 close behind the palpi. Structure of non-marsupial gills as usual. Marsupial 

 portion in the female (PI. XLVI, fig. 4) located in the inner gill, leaving about one- 

 third at the anterior end, and about one-fifth at the posterior end free, so that the 

 marsupium distinctly gravitates toward the posterior i)art of the gill. Interlaminar 

 connections arranged in interrupted septa, and irregular, transverse rows, here 

 and there quincuncial. This irregularly reticulate structure prevails throughout 

 the marsupium, and the septiform arrangement is obscure. 



19. DiPLODON LACTEOLUS (Lea) (1834). 

 See: Diplodon lacieolus (Lea) and D. wymani (Lea) (1860) Simpson, 1914, p. 1226, 

 1230.1" 



" Lea himself (1834, p. 90) has identified the type of Lamarck's U. deloclonta (1819) with his lacieolus 

 (1834, p. 40), but not until after tlie latter name had been published in a satisfactory way, while the 

 original description of delodoiila is absolutely unidentifiable. Thus, according to the rules, larleolufi 

 must be used, as Simpson has done. 



