KONGL. SV. VET. AKADEMIENS HANDL. BAND. 19. N:0 6. 153 



16. Troclius astraliiformis n. 



PI. XIV tig. 54—58. 



Shell conical, tapering to a narrow apex from a broad body whorl. Eight whorls. 

 Their upper boi'der lacerated, as it were, by thick, spinous projections, the /base of 

 which completely conceals the adjoining suture. These processes are formed by reflexed 

 folds of the successive lines of growth, as may best be seen on the umbilical surface 

 of the shell. A little beneath this edge there is a longitudinal bulging out of the 

 whorls. Between the lines of growth the convex surface of the shell is smooth or 

 most finely, transversally striated. The aperture is nearly circular, apiculated in the 

 supei'ior corner, the lips thick and reflexed, the umbilicus is scarcely visible. The 

 sculpture of the umbilical side consists in thick and coarse callous lines of growth at 

 a regular distance from each other. H. 12 millim., br. 18 mill. A few specimens have 

 been , collected at Klinteberg. 



Fam. IX. UMBONIDiE Adams. 



Gen. PYCNOMPHALUS n. ') 



Shell thick, trochiform or globose, the inner Ui) of the ai^erttire with a thick callosity, 

 which like a ridge surrounds the umhilicus. 



This genus has been placed amongst the Umbonidfe in consequence of the callo- 

 sity, which encloses the wide umbilicus. Most of the other genera have the umbilicus 

 completely covered by a far larger callosity as in Umbonium (^ Rotella). 



There is a genus Rotellina De Koninck Faune II, iii p. 92 from the Carboniferous 

 formation of Belgium, which according to the figure given, seems to agree nearly with 

 our, but as the descriptive letterpress expressly states that there is no umbilicus, I 

 have not been sure of the identity and could not i-efer the Gotland species to it. • • 



Pitonellus Montfort has also been placed with the Umbonidse, but they have the 

 umbilicus completely covered up. The same is also the case with Umbonium helici- 

 forme Goldfuss from Paffrath. 



As to the identity of this genus with Platyschisma see below in Pychn. acutus. 



Of the genus Pycnomphalus I have found the following three species in Got- 

 land. 



1. Pycnomplialus obesus n. 



PI. XV fig. 64—67. 



Shell helicoid, with five ventricose whorls in a short spire. There are no orna- 

 ments excepting some indistinct, transverse lines, which are curved backwards. The 

 aperture is circular, the outer lip thin, the inner lip thickened through an accumula- 

 tion of the shelly matter, nearly five times as thick as in the outer lip. The umbilicus 



') Tlvxvng, dense, thick, o/ncpalng, umbilicus. 



K. Vet. Akad. Handl. Band 19. N:o G. 20 



