﻿568 MISS J. DONALD ON GASTEROPODA FROM [Aug. I905, 



Family PLEUROTOMARiiDiB, d'Orb. 



The Palseozoic forms referred to Pleurotomaria require revision, 

 for few, if any, can strictly be placed in that genus. Many new 

 genera and subgenera have been created from ' Pleurotomaria ' by 

 different paleontologists, both in Europe and in America, but 

 they hardly meet all the needs of the case. Hence, it is often 

 difficult to decide to which of the existing divisions a species should 

 be referred ; nevertheless, I feel that caution is necessary before 

 suggesting new ones, until I have been able to review the whole 

 series of forms. 



In describing the shells before me at present this difficulty is 

 evident. The first species mentioned above (p. 567) comes nearest to 

 examples placed in the genus Plethospira, Ulrich l ; not, however, 

 to the type, PI. cassina (Whitf.), but to PI. Semele (Hall), as repre- 

 sented by Ulrich in pi. lxx, figs. 8-10 (op. cit.). This species and 

 also PI. striata, Ulrich (pi. lxx, fig. 7), have less convex whorls than 

 the type, and PI. Semele is moreover ornamented by two keels like 

 the species under discussion, whereas the type has perfectly-smooth 

 whorls. Ulrich remarks {op. cit. p. 1009) that 



' these two species [PL striata and PL Semele] are perhaps not very good 

 examples ; of Plethospira, still, it would be difficult to pick out any important 

 differences.' 



It would, perhaps, be advisable to place them, as well as the Welsh 

 species, in a separate group, for which I would suggest the name 

 Ulrichospira. 



The other three species, Pleurotomaria Lloydii, Sow., PL Groomii, 

 sp. nov., and a fragment hardly sufficient to identify, most nearly 

 resemble shells referred to Bembexia, (Ehlert. 2 This genus is distin- 

 guished from Ptychomphalus, Agass., by its more turriculated form, 

 more angular whorls, and by having the band situated on the summit 

 of the angle and at a little distance from, instead of immediately 

 above, the suture. (Ehlert further distinguishes it by stating that 

 the columellar border is thickened and the band wide. 



The three species here described are turriculated, and the band is 

 situated on the angle of the whorls, a little distance above the suture. 

 They none of them show the columellar border, and the band is of 

 moderate width : it could hardly be called wide in any of them, 

 except perhaps in Bembexia (?) Groomii, where it is tolerably wide 

 in proportion to the shell. 



Ulrich refers Pleurotomaria (Bembexia ?) Lloydii (op. cit. p. 1012) 

 to his genus Seelya, but it is distinguished from the members of 

 that genus by possessing a slit in the outer lip, by more oblique 

 lines of growth, and by the band being narrower. The lines of 

 growth appear to be more oblique than those of the other two 



1 Final Eep. Geol. & Nat. Hist. Surv. Minnesota, vol. iii, pt, ii (1897) 

 p. 958. 



2 ' Descriptions de quelques Especes devoniennes du Departement de la 

 Mayenne ' p. 24 (Extrait du Bull. Soc. d'Etudes Seientifiques d' Angers, 1887). 



