1899.] NATURAL SCIENCES OF PHILADELPHIA. 173 



T. Dalli Bush — wh. 12 + the transverse, projecting nucleus; ribs 



26. ^ X 2| mm. 

 T. Hemphilli Bush — wh. 12 + the transverse, projecting nucleus; 



ribs 20. 9+ X 2 mm. 

 T. Swlftii Bush— wh. 13-17 + the oblique, projecting nucleus; 



ribs 20-26. 6-7+ X 1 mm. 

 T. exarata (Lea) — not Mentstho exarata A. Ad., 1861 — wh. 15 



with nucleus; ribs about 22. 



B. — Transverse ribs not always reaching perij)heryof body-whorl; 

 ribs ill -defined. 

 T. atypha Bush — wh. 10 + (nucleus wanting); ribs 20. 7^+ X 1| 



mm. 

 T. Uruguayensis Pilsbry — Avh. 11 + the transverse, very projecting 



nucleus; ribs about 26. 10.3 X 3 mm. 

 T. helotheca Dall — wh. 15 + (nucleus wanting); ribs about 20. 



14X3 mm. Deep water. 



2.- SPIRALS PRESENT. 



A. — Transverse ribs ending at peri2:)hery of body- whorl; base 

 usually smooth ; spirals = raised, rounded threads. 

 T. reticulata C. B. Adams — wh. 7 + the very oblique, flattened nu- 

 cleus; ribs 26-30; threads coarse, distant, decussating the ribs. 



.125 X .04 inches. 

 T. multicostata C. B. Adams — wh. 9 + the very oblique, flattened 



nucleus; ribs 34-38; threads coarse, distant, traversing the ribs 



on their lower portion. .165 X .045 inches. 

 T. unilirata Bush — ^Yh. 9 + the transverse, projecting nucleus; 



ribs 20-24; 1 thread just below suture. 3 J X about ^ mm. 



B. — Transverse ribs ending at periphery of body-whorl ; base 

 sculptured ; spirals —. incised lines ; no spirals above. 

 T. /it rWs d'Orbigny — wh. 14, with oblique, flattened nucleus; rib.s 



about 22 ; intercostal spaces smooth ; base spirally striated. 7 X 



1^ mm. 



B'. — Transverse ribs ending at j^eriphery of body-whorl; base 

 usually sculptured ; spirals above. 



a. — SPIRALS COARSE, EQUAL OR NEARLY SO = Pyrgostelis Mon- 



terosato, 1884. Type, T. rufa Philippi. 

 T. virga Dall — wh. 10 + (nucleus wanting) ; ribs about 20; spirals 

 = 7 lines on intercostal spaces. 6 X IJ mm. 



