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



Oriostoma (pars), G. Lindstrom (non Munier-Chalmas), 1884, ' Silurian Gastropoda 

 & Pteropoda of Gotland ' Kongl. Svensk. Vet.-Akad. Handl. vol. xix, No. 6, 

 p. 156. 



OmplialotrocTius, K. A. Zittel, 1896 (non Meek, 1864), ' Text-book of Palaeont- 

 ology ' translated by C. P. Eastman, vol. i, pt. i (1900) p. 447. 



Diagnosis. — Shell discoidal, or depressed conical; spire short. 

 Whorls convex, contiguous, ornamented by spiral keels and threads. 

 Aperture subcircular ; lips thin, generally continuous. Operculum 

 thick, flat internally, conical externally. Umbilicus open, wide. 



Type, Polytropina discors (Sow.). 



Remarks and Resemblances. — In 1881 L. G. de Koninck 

 gave the name Polytropis to a group hitherto included in Euom- 

 phalus, taking E. discors, Sow., as the type. It is distinguished 

 from the typical Euomphalus by having no sinus in the outer lip. 

 Unfortunately the name was preoccupied, for it had been given 

 by C. L. U. Sandberger to a subgenus of Valvata in 1874. 1 

 De Koninck considered Polytropis identical with Inachus, Hisinger, 

 but this name had been previously used by Leach. I therefore 

 suggest the name Polytropina for the genus. 



Lindstrom referred Euomphalus discors and other allied forms 

 to Oriostoma, Munier-Chalmas; 2 but this genus, as described by 

 Munier-Chalmas, is quite distinct, for the whorls of the spire and 

 the umbilicus are disjoint, and the last whorl is very much larger 

 than the others. Munier-Chalmas considered his genus to have 

 affinity with certain species placed in Platyceras and Tuba. 



Zittel referred Euomphalus discors, Sow. and E. globosus (Schloth.) 

 to Omphalotrochus, Meek, 3 which genus he considered identical 

 with Polytropis, de Kon. and Oriostoma, Lindstrom, but not with 

 Oriostoma as originally defined by Munier-Chalmas. Euomphalus 

 Whitney^ the type of Omphalotrochus, appears to me quite distinct 

 in its characters from either E. discors, Sow. or E. globosus 

 (Schloth.), the whorls being ornamented by only two keelson the 

 periphery, which give them a banded appearance; they are 

 also flattened above and below, instead of being convex ; the 

 aperture is different ; and the shell appears to have more in 

 common with Trochonema. Solarium antiquum, 4 ' A. d'Orbigny, 

 the other species referred by Meek to his genus, seems to agree 

 with Euomphalus Whitney i, but is quite distinct from E. discors 

 and E. globosus. 



Polytropina globosa (Schloth.). (PI. XXXVII, fig. 16.) 



TrocMlites globosus, Scblotheim, 1820, ' Die Petrefactenkunde ' p. 162. 

 JSuomplialus funatus, J. de C. Sowerby, 1823, 'Mineral Conchology' vol. v, p. 71 

 & pi, ccccl, figs. 1-2. 



Diagnosis. — Shell conical; spire somewhat depressed, of about 



1 'Die Land- & Siisswasser-Conchylien der Vorwelt ' p. 697. 



2 Journal de Conchyliologie, vol. xxiv (1876) p. 103. 



3 ' Geol. Surv. California : Palseontology ' vol. i (1864) p. 15 & pi. ii, figs. 8-8 a. 



4 ' Voyage dans l'Anierique Meridionale ' vol. iii, pt. iv, Paleontologie 

 (1842) p. 42 & pi. iii, figs. 1-3. 



