74 G. LINOSTIiÖM, ON THE SILURIAN GASTROPODA AND PTEROPODA OF GOTLAND. 



of a species with considerably enlarged aperture and narrow whorls, representing the 

 division of Bellerophoiis named Phraginostoraa, which are of such frequent occurrence 

 in the Upper Silurian shale beds of Scania. Bnt they are too obscure for Identification. 



Conspectus of the Species: 

 I. Shell only with transverse stria>, radiating in pinnate arrangement from the 

 slit band: 



1 B. sphsera n. 



2 B. fasciatus n. 



3 B. globulus n. 



4 B. tajnia n. 



5 B. fastigiatus n. 



6 B. tubulosus n. 



II. Shell with longitudinal stria^ or furrows intersecting the transverse ones ( = 

 Bucania Waagen and De Koninck). 



7 B. squamosus n. 



8 B. Eiseni n. 



9 B. elegantulus n. 



10 B. latevittatus n. 



11 B. gemma n. 



12 B. pilula n. 



III. Shell divided through two longitudinal grooves. 



13 B. trilobatus Soav. 



1. Bellerophon sphsera n. 



Pl. III %s. 35—38, pl. Y figs. 1—16, pl. VII fig. 9. 



Shell globular, extreraely thin. Surface ornamented by closely set, transverse striaB, 

 which abut iipon the slit band in an acute angle of 45° and curve gently ontward 

 in a bow, the convexity of which is directed towards the aperture. There is some 

 variation, as shown in the figures, with larger, smooth intervals between the striaj. 

 Some faint longitudinal stria? crossing them are visible in several specimens. In well 

 preserved shells and through sections in the umbilicus it is evident that raany of the 

 transverse stria3 have continued as free, outwardly bent, thin laminae. They have been 

 especially crowded in the umbilicus, where they also are most completely preserved^ 

 imbedded in the soft shale. Several figures are given on plate V, showing details in 

 natural size and magnified- Their length amounts to two millimeters and sometimes 

 inore. Where they have been well protected they stånd ont in relief as nari-ow hooks. 

 These lamellee have probably, each in its turn, been the apertural börder of the widely 

 expanded mouth. 



The whorls are five and a half, much rounded, and, as seen In transverse sec- 

 tions, from two to three tiraes as broad as high. The last whorl is much expanded near 

 the aperture, with the slit band elevated as a blunt keel. The aperture is large, trans- 

 versally obovate, the lips rather thick. the inner lip bent down as to hide the whorl 



