786 PROCEEDINGS OF THE ACADEMY OF [DeC, 



Specimens from Acambaro, State of Guanajuato, are similar, two 

 measuring: length 12, alt. 9, diam. 7 mm., and 10.2, 8, 6 mm. 



The species described from Ameca, Jalisco, under the name *S'. 

 luridum j\Iarts." seems to be very near S. triangulare, if not actually 

 identical therewith. 



Sphaerium martensi Pilsbry. PI. LIII, figs. 2, 2a : PI. LIV, fig. 4. 



Proc. Acad. Nat. Sci. Phila., p. 401, 1899. Biologia, p. 552. 



When cleaned of the ferrous deposit which coats this shell, it is light 

 yellow, becoming pinkish-gray in the neighborhood of the beaks. The 

 sculpture is a very fine, sharp striation over the lower two-thirds, the 

 l^caks being nearly smooth, with minute, glossy tips, sometimes 

 slightly marked off by a barely perceptible depression. The differ- 

 entiation of the prodissoconch seems hardly tangible enough to war- 

 rant a reference of the species to the subgenus J\[uscuUum, and, 

 moreover, the shell while thin is not fragile as in MuscuUimi. 



The cardinals are double in the right valve (PI. LII, fig. 2), as 

 well as the laterals. The latter are rather small and low, and not 

 crenulate. In the left valve the lateral teeth are single. The shell 

 is less solid than S. triangulare, but decidedly stronger than S. suh- 

 transversum. It does not seem very closely related to any other 

 species. Length 15.6, alt. 11, diam. 7.7 mm. 



Known only from the type locality, Tzintzimtzan. Lake Patzcuaro, 

 State of Michoacan. 



Sphaerium jalapensis n. sp. PI. LIII, figs. 1, la; PI. LIV, fig. 3. 



Shell oval, somewhat compressed, the diameter about half the 

 length; ends almost equally rounded, but the anterior is a little more 

 narrowly so; upper and basal margins equally arcuate; beaks pro- 

 jecting but slightly above the dorsal margin; glossy, finely, irregularly 

 striate, and very minutely rugose or subgranulate. There are also 

 obscure radii visible in a suitable light. Olivaceous-gray with a yellow 

 border, and fully adult shells are bright chestnut-colored toward the 

 eroded apices. Escutcheon narrow, lanceolate and perceptibly flat- 

 tened or excavated; lunule indistinct. Interior bluish-white. 



Right valve (PL LII, fig. la) with a small, oblique, bifid anterior 

 and minute posterior cardinal tooth; anterior laterals double, strong, 

 elevated and triangular; posterior laterals double, more slender and 

 crenulate. Left valve (PI. LII, fig. 1) w^ith a bifid posterior and 

 small simple anterior cardinal; laterals single, the anterior short, high 

 and triangular; posterior lateral single, more compressed. 



" Biologia Cenfr. Amer., Moll., p. 552. 



