28 PALEONTOLOGY OF NEW-YORK. 



GEN0S RAPHISTOMA. 



[Greek pass, a seam or suture, and rfTofjia, mouth ; from the suture or seam-like appearance in the uppei 



side of the aperture.] 



Character. Shell depressed-turbinate ; discoidal spire, with three to five volutions ; suture 

 close ; umbilicus moderately large ; aperture subtrigonal ; upper side of the volutions 

 marked by a kind of seam or suture, produced by the sudden tendency backwards of the 

 striae, which leaves a slight notch in the edge of the aperture. 



This genus approaches to Euomfhalus in some of its. characters, while it possesses others 

 in common with Pleurotomaria. The slight notch in the upper edge of the aperture, 

 which is marked in the progressive growth of the shell by a simple seam or bending in the 

 striae, is somewhat similar to the notch and band of Pleurotomaria ; but the outer angle 

 of the volution presents no band, but a simple bending of the striae. It is probable also that 

 the generic characters here given may be so extended as to include the Scalites figured 

 above, as I have some evidence of the existence of the characteristic markings upon that 

 shell. 



The species now described have heretofore been referred to Maclurea, but the characters 

 are different from the typical species of that genus. 



48. 1. RAPHISTOMA STRIATA. 



Pl. VI. Figs. 2 a, b. 



Maclurea striatics. Emmons, Geol. Report, 1842, pag. 312, fig. 3. 



Machirea labiata? (A cast). Ibid. fig. 2. 



Euomphalus gvnlterialus? Goldfuss, 1834; and 1844, Vol. 3, pag. 81, pl. 1S9, fig. 3. 



Compare Euomphaliui gua/terialus. Verneuil, Palieontology of Russia and the Ural Mountains, 1845,. 



pag. 333, pl. 23, fig. 1 a, b. 

 And Euumphnhis pseiido-gualteriatns. Hisinger, Lethaea Suecica, 1837, pag. 36, pl. 11, fig. 5. 

 Not Pleurotomaria hnticularis. Emmons, Geol. Report, 1842, pag. 393, fig. 2. 



Depressed, discoidal ; breadth twice as great as the height ; spire nearly flat, slightly 

 elevated towards the apex from the inner side of the last volution ; volutions about four or 

 five, somewhat rapidly diminishing towards the apex, ventricose below ; outer margin 

 obtusely angular ; aperture subtriangular, nearly straight above and rounded below : 

 umbilicus luodcrately large. 



The specimen figured is somewhat imperfect ; a portion of the surface only being covered 

 by stria', which are round and rather coarse. Though apparently not identical with the 

 figures of Goldfuss referred to, or with the original Helicites qualteriatus of Schlotheim 

 {JVac/Urdgen, Pl. xi. fig. 3) , it is nevertheless to be regarded as a representative species ; 

 and being found in tlie Lower Silurian strata {Strata calcarea antiquiora, Hisinger) of 

 Europe, it becomes interesting to inquire whether it may belong to some representative 

 mass of the Chazy limestone, as our fossil is unknown in any higher position. 



