INVERTEBRATE PALAEONTOLOGY. 553 



Genus THAUMASTUS, Albers. 



Si/non. — Bulimus fap.),of many authors. 



Thaumastus, Albers (1860), Die Heliceeu, von Marten's ed., 215 (proposed as a subgenus under 

 Bulimulua).— Tryon (186G), Am. Jour. Conch., Ill, 1G7 and 170 (as a genus).— Binney 

 (1869). Land and Fresh-water Shells of N. Am., part I, Pulmonata, 199 (as a subgeuus 

 under HiiJimitlus). 



FAym. — i9av/ia<7rof, strange. 



Type. — Bulimus Sarttvegi, Pfeiffer. 



Shell narrow-subovate to ovate-subfusiform, imperforate or rimate; 

 surface nearly smooth, in the recent state whitish, sometimes variegated with 

 brown dashes or stripes; aperture ovate; outer lip obtuse, straight or 

 slightly expanded; inner lip reflexed, and more or less appressed ; columella 

 twisted. 



This group is generally regarded as a subgenus under Bulimulus, where 

 it was ranged by Albers as the sixth of nineteen sections recognized by him 

 under that group. I do not pretend to have thoroughly investigated these 

 groups ; but it seems to me, practically at least, more convenient to use this 

 section as a distinct genus, as has been done by Mr. Tryon. 



In regard to the geological range of this genus, little can be said. The 

 species hereinafter described came from beds apparently of older Eocene 

 age. Several species resembling this group have been, figured from rocks of 

 that and later Tertiary ages at different foreign localities. The genus, how- 

 ever, seems to attain its greatest development at the present time. Albers 

 enumerates under it fourteen recent species, exclusive of three or four others 

 included by Mr. Tryon, who ranges six North American species in this group. 

 The recent species seem to be all American, and occur in both North and 

 South America ; those found in North America occur in Mexico, Texas, and 



California 



Th a ii mast us limnaeiformis, M. & H. 



Plate 44, figs. 8, a, u, c, d. 



Bulimus limnaeiformis, Meek and Hayden (1856), Proceed. Acad. Nat. Sci. Philad., VIII, 118. ' 

 Bulimus Xetrasccnsis, Meek and Hayden (1856), ih. 



Shell small, narrow-subovate, rather solid ; spire moderately elevated, a 

 little obtuse at the immediate apex; volutions five to six, moderately convex; 

 suture distinct: surface polished, and only marked by very fine, nearly obso- 

 lete lines of growth; aperture narrow-subovate, a little oblique, angular 

 above and narrowly rounded below, usually a little shorter than the spire; 

 70 H 



