DESCRIPTIONS OF SPECIES. 453 



granda&va and PL gi^anvillensis have not been figured at all, nor the surface of PI. 

 primaria, it is impossible to form a just estimate of this character or of their affinities. 

 PI. granviUensia may belong in the annuUstriata group. The two other species 

 probably go with PI. meehiana. I am in some slight uncertainty as to the proper 

 location of PI. canna. If it is marked by longitudinal strife, as White's description 

 states, it belongs without doubt to Dentalium, but in the type specimen there are no 

 indications of such stri^ which are not so faint and so occasional that thej^ might not 

 be due to chance or to expectant imagination. As the transverse growth lines are 

 clearly preserved in one specimen, it would seem that the longitudinal markings also, 

 if present, would be visible. For this reason I place Pentalium canna with Plagio- 

 glypta in the meehiana group. 



Plagioglypta venusfa and PI. UUyioisensis are described as having a smooth 

 surface, and constitute what may be desirable to separate as a distinct subdivision 

 and designate the venusta group. At the famous Spergen Hill localitj" occurs in 

 some abundance a dentalioid shell, probablj' PI. venusta, whose surface appears to 

 be entirely without markings. Whether its characters have been obscured or 

 destroyed by attrition or fossilization I find myself at present unable to decide. 



The surface of PL anmdistriata is in strong contrast to that of PL meeTciana, 

 although the difference is one of degree merely. Intermediate between them in this 

 particular stands PL undulata, the t3-pe of Plagioglypta, and- Dr. Pilsbr}^, whom I 

 have had the honor to consult in this matter, advises me that, according to its 

 original extension, both Carbonifei'ous forms can be admitted into his genus. 



It still remains a debatable question what sho ild be done with the vemista type. 

 It certainly does not appear to have the characters of Plagioglypta, much less of 

 Pentalium, and if what is recorded of this species and of PL illinoisensis is veri 

 table, neither can properly be admitted into either of tliese genera. It is doubtful 

 if Lsevidentalium ranges back into Paleozoic time, and it therefore seems inadvisable 

 to place them with that genus. Perhaps the course open to the least objection is to 

 refer them as a separate and doubtful subdivision to Plagioglypta pending the 

 absence of determinative data. 



GASTEROPODA. 



EUCONISPIRA Ulrich, 1897. 

 EucoNispiRA TAGGARTi Meek. 



PL X, figs. 9, 9a. 

 1874. Plenrotomuria taggarti. Meek, U. S. Geol. Geog. Surv. Terr., [Seventh] Ann. Rept., for 1873, 

 p. 231. 

 Carboniferous: Canyon of Four-Mile Creek, Colorado. 

 1880. Pleurotomuria tarjgerti. White, U. S. Geol. Geog. Snrv. Terr., Twelfth Ann. Rept., for 1878, pt 1, 

 p. 140, pi. 34, figs, la, b. 

 Carboniferous: Near Horseshoe Mountain, South Park, Colo. 



