788 PROCEEDINGS OF THE ACADEMY OF [DeC, 



obliquely subtruncate; upper and lower margins subcqually arcuate; 

 beaks full and prominent, with rather indistinct "caps"; lunule and 

 escutcheon are not differentiated. Surface glossy, finely and rather 

 obsoletely striate. Yellowish-gray. Interior bluish-white. Right 

 valve (PI. LIII, fig. 5), with two small diverging cardinal teeth, and 

 double anterior and posterior laterals, the former stouter. Left valve 

 with the cardinal tooth small, the laterals single. 



liCngth 11, alt. 9, diam. 6 mm. 



Monterey, State of Nuevo Leon. Types No. 77,190, A. N. S. P., col- 

 lected by S. N. Rhoads, 1899. 



This species is similar to S. partumcium in general characters. The 

 beaks are not distinctly capped as in that species, and the anterior 

 lateral teeth are shorter and much closer to the cardinal. 



In my opinion the shells figured by Crosse and Fischer as S. suh- 

 transversum belong to this species. 



Pisidium abditum Hald. 



Lake Prassa, near Uruapam, and Tlalpam, State of Mexico; Texolo, 

 State of Vera Cruz (Rhoads) ; also Orizaba, V. C. (Heilprin expedi- 

 tion) . These localities go far to connect the Central American range 

 given by v. Martens with the range of the species in the United States. 



UNIONID^. 

 TJnio plexus Conrad. 



\'era Cruz, State of Vera Cruz. 

 Lampsilis umbrosus (Lea). 

 Vera Cruz, V. C. 



Lampsilis rovirosai Pils. PI. LIV, figs, l, la. 

 Nautilus, XIII, p. 140 (April, 1900). 

 Laguna de Atasta, near San Juan Bautista, State of Tabasco, col- 

 lected by Sr. Ing. D. Jose N. Rovirosa, a naturalist of Tabasco, espe- 

 cially interested in botany, whose death, December 23, 1901, I regret 

 to record. The figures are natural size, from photographs of the type. 

 No. 58,916, A. N. S. P. 



Reference to Plates XLVII-LIV. 



Plates XLVII to LIII loere drawn with camera lucida by 



Miss Helen Winchester; plate LIV was repro- 



' duced from photographs. 



Plate XLVII, Figs. 1, la — Glandina viichoacanensis Pils. 

 Fig. \h. — New-born young of the same. 

 Figs. 2, 2a, 26. — Glandina huingensis Pils. 

 Figs. 3, 3a, 36. — Glandina rhoadsi Pils. 

 Figs. 4, 4a, 46. — Glandina victor iana Pils. 

 Figs. 5, oa. — Glandina dalli Pils. 



