C. D. Walcott — Paleozoic Pteropods. 17 



Art. IT. — J\ T o/e on some Paleozoic Pteropocls ; by Charles 

 D. Walcott, of the U. S. Geological Survey. 



It is with considerable reservation that I place the genera 

 Conularia, Hyolithes, Hyolithellus, Coleoprion, Coleolus, Hemi- 

 ceras, Salterella, Pterotheca, Phragmotheca, Matthevia and per- 

 haps Palasnigma under the Pteropoda. They form a group 

 that, although representative, in a measure, of the recent Ptero- 

 poda, differ in other respects so much that it appears as though 

 a division of the Gasteropoda, equivalent to the Pteropoda, 

 might be consistently made to receive them. 



I have had in my possession for two years past the speci- 

 mens on which the genera Matthevia is founded, and it is of 

 such interest that I take the opportunity of publishing it 

 before bringing out the illustrations of the fauna with which it 

 is associated. 



Genus Matthevia, n. gen. 



Shell conical, aperture sinuous, transverse section ovate, 

 elliptical or rounded subquadrate ; interior with two elongate 

 chambers diverging from the apex and opening into a large, 

 single, terminal chamber; both of the interior chambers are 

 crossed by a single imperforate septum; calcareous; surface 

 papillose. Operculum calcareous, nucleus excentric, lines of 

 growth concentric. 



Type Matthevia variabilis. 



The generic name is proposed in honor of Mr. G. F. Matthew, 

 who is doing so much good work on the St. John fauna. 



This peculiar shell is so distinct from all described forms 

 referred to the Pteropoda, that a new family, Matthevidas, is 

 instituted to receive the one genus now known. 



In form and surface markings it approaches the genus Conu- 

 laria; the operculum maybe compared to that of Hyolithes, 

 and the imperforate transverse septum allies it to both Hyolithes 

 and Conularia. Its thick shell is observed in the genera Conu- 

 laria, G. fecunda Barr. (Syst. Sil. Boheme, vol. iii, pi. viii, fig. 8), 

 and Hemiceras, H. cylindricus Eichwald (Leth. Hoss., vol. i, Atlas, 

 pi. xl, fig. 17 ; pi. xlii, fig. 29). When we come to trace a 

 relationship to the two inner chambers, we are, at once, at a 

 loss for comparisons. 



There is a curious form described as Tetradium* Wrangeli 

 Schmidt (Mem. Acad. Imp. Sci. St. Petersbourgh, VII. Ser., 



* The genus Tetradium being preoccupied (Dana, 1846 ; Safford, 1856), I pro- 

 pose Palaenigma in place of Schmidt's Tetradium, 1874, for the species under con- 

 sideration — P. Wrangeli. 



A.m. Joue. Sci. — Third Series, Vol. XXX, No. 175. — July, 1885. 

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