GASTROPODA. 1067 



* 



H"|.OPKA r.xcEixA, H. .-/ . 



i I MK l.\\i\. FIGS. II and IJ. 



Similar //. ronriiuni/u but larger and relatively higher In the spire, with the aperture more 

 olilii|U(* <a>ut a- In //. rotunda), the whorl* scarcely to ventrlcose, and the umbilicus much smaller and 

 probably closed entirely In the shell. Perhaps It In not distinct from //. paludmiforntit Hall, but If we 

 may rely on Hall's tlgurs of that shell, It differs, excepting the umbilicus, from //. exetlta about a.s //. 

 ronctfinufa doe*. 



Fiirmation and toeaitty. Fusliplrt bed of the Trenton group, WykolT, Sunnier and Under, Minnesota. 



CbOseMoM. Geological and Natural History Survey of Minnesota; E. O. Ulrlch. 



Jfmnmi .Register, No. 286. (A crushed specimen somewhat doubtfully referred to this species.) 



HOLOPKA PALUDINIFORMIS Hull. 

 (Not figured.) 



JfefepM pehdtntfo* HALL, 1847, Pal. N. Y., vol. 1, p. 171, pi. xxxvu, figs. So, 36. 



A small specimen, apparently of this species, was collected by Mr. B. O. Ulrlch In the Clltambonltes 

 bed of the Trenton group near Cannon Falls, Minnesota. The specimen Is Imperfect at the mouth and 

 shows clearly that It ha* a small umbilical perforation, so It may belong to some other species, unless the 

 prevailing Impression that H. paludiniformi* has no perforation proves erroneous. With this specimen a 

 larger one was found which poMlbly Is the same. We think not, however, since It has a wider umbilicus 

 and an Impressed suture, reminding one In both features of H. nppntta. 



HOLOPKA PYKKNB Billings. 



PLATE LXX1X. KIU8. U-IS. 



llotopta pyrene HILLINGS, 1862, Pal. Foss., vol. I, p. ft. 



llolopta ^enntdoM SAROBSON, 1802, Bull. Minn. A cad. Nat. Set., vol. Ill, p. 336. 



. obliquely turbiuate, spire depressed conical, rising but little above the top of the last whorl; 

 whorls three or four, the Inner ones appearing slender, the last somewhat ventrlcose, subovate In cross 

 section, the vertical diameter considerably greater than the transverse, the upper side of the outline more 

 obtuse than the lower; umbilicus large; suture deeply Impressed; aperture slightly oblique; whorls crowed 

 by deep concave undulations separated by rather sharp ridges; lines of growth very obscure In the speci- 

 mens studied, which seem to be, at least In part, caste of the exterior. Width 33 mm., hlght about 

 27 mm. 



It may be that Dr. Sardeson was Justified In separating the Minnesota species here described from 

 //. pyrmt, especially since Billings says that his specimen, which does not show the under tide, has a form 

 " much like H. obliqua Hall," and comes from a lower geologic horizon than our specimens. It has, how- 

 ever, seemed so unlikely to us that such an extravagant character as the strong undulations of the whorls 

 would appear In two distinct species f the same genus, that we have decided to refer the Minnesota spec- 

 Imeos to Billings' species until the latter has been shown to be distinct. 







Formation and ioeaUiy. Lower part of KuMspira bed. near Cannon Falls, Minnesota. 

 CWkctioit.-E. O. Ulrlch. 



II'M.OPKA PAKVri.A. . if. (UHch.) 

 PLATE LXXIX. no. IS. 







: small, to 10 mm. In width, the hlght equalling about three-fourths of the width; spire 

 depressed conical; whorls four, Including two very small ones at the apex, neatly rounded, subclrcular In 



