1903.] NATURAL SCIENCES OF PHILADELPHIA. 789 



Fig. 6. — Glandina oblonga tamaulipensis Pils., young shell. 

 Figs. 6a, 66. — Glandina oblonga tamaulipensis Pils. 



Plate XLVIII, Figs. 1, la, lb. — Glandina delicata Pils. 

 Fig. 2. — Glandina delicata alticola Pils. 

 Figs. 3, 3a. — Streptostyla novoleonis Pils. 

 Figs. 4, 4a. — Succinea tlalpamensis Pils. 

 Figs. 5, 5a, 5b. — Omphalina montereyensis victoriana Pils. 

 Figs. 6, 6a, 66. — Omphalina montereyensis Pils. 

 Figs. 7, 7a, lb. — Omphalina martensiana Pils. 



Plate XLIX, Figs. 1, la, lb. — Pyramidula victoriana Pils. 

 Figs. 2, 2a. — Thysanophora proxima Pils. 

 Figs. 3, 3a, 36. — Thysanophora tatei Pils. 

 Fig. 4. — TrochateUa simpsoni Anc. Topotype. 

 Figs. 5, 5a, 56. — Guppya micra Pils. 

 Figs. 6, 6a. — Thysanophora fischeri Pils. 



Plate L, Fig. 1. — Pseudosubulina occidentalis Pils. 

 Fig. 2. — Pseudosubulina texoloensis Pils. 

 Fig. 3. — Opeas odiosum Pils. 

 Fig. 4. — Opeas rhoadsce Pils. 

 Fig. 5. — Opeas patzcuarense Pils. 

 Figs. 6, 6a. — Spiraxis{?) borealis Pils. 

 Figs. 7, 7a. — Bifidaria prototypus Pils. 

 Fig. 8. — Leptinaria tamaulipensis Pils. 

 Figs. 9, 9a. — Spiraxis uruapamensis Pils. 

 Figs. 10, 10a. — Epirobia mirabilis Pils. 



Plate LI, Figs. 1, la, 16. — Polygyra suprazonata Pils. 

 Figs. 2, 2a, 26. — Polygyra rhoadsi Pils. 

 Fig. 3. — Schasicheila minuscula Pfr. 

 Fig. 4. — Schasicheila vanattai tricostata Pils. 

 Figs. 5, 5a. — Schasicheila vanattai Pils. 

 Figs. 6, 6a. — Praticolella strebeliaiia Pils. 

 Figs. 7, 7a. — Schasicheila fragilis PUs. 

 Figs. 8, 8a. — Schasicheila hidalgoana Dall. 



Plate LII, Fig. 1. — Sphoerium jalapense PQs., left valve; la, right valve. An- 

 terior teeth are reversed in this specimen. 

 Fig. 2. — Sphcerixim martensi Pils. Right valve. 



Fig. 3. — Sphcenum triangulare Say. Right valve. Lake Patzcuaro. 

 Figs. 4, 4a. — Chondropoma martensianum Pils. 

 Figs. 5, 5a. — Valvata humeralis pilsbryi Marts. 

 Figs. 6, 7, 8. — Pyrgtdopsis patzcuarensis Pils. 

 Fig. 9. — Valvata humeralis. Lake Xochimilco. 

 Fig. 10. — Amnicola tryoni Pils. 



Fig. 11. — Amnicola panamensis Tryon. Type specimen. 

 Fig. 12, 12a. — Valvata humeralis Say. Type specimen. 



Plate LIII, Figs. 1, la. — Sphcerium jalapense Pils. 

 Figs. 2, 2a. — Sphcerium martensi Pils. 



Figs. 3, 3a. — Sphcerium triangulare Say. Lake Patzcuaro. 

 Figs. 4, 4a. — Sphcerium triangulare Say. Type specimen. 

 Figs. 5, 5a, 56. — Sphcerium novoleonis Pils. 

 Figs. 6, 6a, 66. — Sphoerium subtransversum Prime. 



Plate LIV. — Figs. 1, la. — Lampsilis rovirosai Pils. 



Fig. 2. — Sphcerium triangulare Say. Lake Patzcuaro. 



Fig. 3. — Sphcerium jalapensis Pils. 



Fig. 4. — Sphoerium martensi Pils. 



Fig. 5. — Sphcerium subtransversum Pme. 



Fig. 6. — Sphoerium novoleonis Pils. 



Figs. 7, 8. — Helicina sowerbyana Pfr. 



