2S 



Over deo hele arktiske Zone synes denne Art at 

 vaie talrig udbredt i de middelmaadige Dyb. Prof. Leche 

 angiver den fra det Kariske Hav 1 . 



Hvorvidt Cingula Jan Mayeni, Verrill er vor Art, 

 betvivler jeg. Prof. Verrill har været saa venlig at sende 

 mig Exemplarer af den amerikanske Form, men disse 

 adskiller sig fra vor ved en paafaldende grovere Sculptur. 

 Spiralribberne er saaledes kun 3 til 4 og af betydelig 

 Styrke, hvorved Skallen faar Udseendet af at være 3 — 4 

 carineret. Ved at sammenligne Verrills Tegning (Cat. 

 Mar. Moll. 1882, Pl. XLII, Fig. 8) med, vor, vil denne 

 Afvigelse være ioinefaldende. For at adskille disse to For- 

 mer vil jeg derfor foreslaa Rissoa americana for den ameri- 

 kanske Form. 



Rissoa (Cingulai islandica, n. sp. 



Tab. XI. Fig. 8, 9. 



Skallen gjennemsigtig hvid, svag glindsende, eylindrisk 

 conisk, Vindingerne 5 svagt convexe. Suturen dyb; Mund- 

 aabningen omtrent 3 / 7 Del af Skallens Længde, rund oval. 

 unget udvidet nedad og noget skjæv; ydre Læbe noget for- 

 tvkket. den indre vel udviklet og sammenhængende ; der er 

 en tydelig Umbilicalsplit. Sculpturen bestaar af yderst 

 tine. næsten microscopiske Spiralstriæ og svage, men tætte 

 Vækststriber; Apex er stump, glat og glindsende. 



Størrelse: 2 1 //"" Axiall.. I 1 ,.,""" Diam. 

 Forekomst: St. 48— 299 Favne. 1 levende Expl. 



Dr. Jeffreys antog vor Art for muligens at være en 

 Dybvandsvarietet af Rissoa a/renaria, men denne Anskuelse 

 kan jeg ikke dele, da den forekommer mig altfor afvigende 

 baade i Form og Sculptur. Cingula l&ptalea, Verr., synes at 

 stan den meget nær, men Mundaabningeus Form er afvigende. 



Rissoa (Setia) Griegi, Fr. 



Tab. XI. Fig. 10. 



Bissoa Griegi, Kri. 'le. Jahr!). Mal. Gesell. 1879, Pg. 274. 

 Skallen rund oval. næsten globos, gulagtig, Vindin- 

 gerne 4 tumide. raskt tiltagende. Spiret kort. Suturen dyb; 



1 Herzenstein (op. c. Pag. 682) angiver .len fra det hvide Hav. 



This species appears to lie abundantly distributed 

 over the whole arctic zone, in moderate depths. Prof. 

 Leche states it as pertaining to the Kara sea 1 . 



I have some doubt whether Cingula Jan Mayeni, 

 Verrill, is our species. Prof. Verrill has kindly sent me 

 specimens of the American shell, but it is distinguishable 

 from ours by a strikingly coarser sculpture. The spiral 

 ribs are, for instance, only 3 to 4 in number and of consider- 

 able strength, owing to which fact the shell acquires the 

 appearance of being triply to quadruply carinated. On 

 comparison of Verrills illustration (Cat. Mar. Moll. 1882, 

 PI. XLII, fig. 8) with ours, this divergence becomes im- 

 mediately apparent. In order to distinguish these two 

 forms I would, therefore, propose as an appellation for 

 the American form. Rissoa americana. 



Rissoa (Cingula) islandica, n. sp. 



PI. XI, figs. 8, 9. 



The shell translucently white, faintly lustrous, cylin- 

 dric-conical; 5 faintly convex whorls; the suture deep; the 

 aperture measuring about three-sevenths of the length of the 

 shell, subcircular, somewhat dilated outwards and a little 

 oblique; the outer lip somewhat thickened; the inner lip 

 well developed and continuous: there is a distinct umbili- 

 cal fissure. The sculpture consists of extremely tine, almost 

 microscopical, spiral striæ, and of faint, but close lines, of 

 growth. Apex, obtuse, smooth and lustrous. 



Size: Axial length. 2..V"'", Diam. 1 .5 



Habitat: Stat, No. 48. Depth, 299 fathoms. One 

 living specimen. 



Dr. Jeffreys considered our species to be, probably, 

 a deep-water variety of Rissoa arenaria, but I cannot share 

 that opinion, as it appears to me to be too divergent both 

 in form and sculpture. Cingula leptalea, Verr. appears to 

 be related to it, but the form of the aperture differs. 



Rissoa (Setia) Griegi, Fr. 



PI. XI, Fii--. 10. 



Rissoa Griegi, Friele. Jahrb. Mal. Gesell. 1879. pag. 274. 



The shell subcircular, almost globular, yellowish; 4 



tumid, rapidly increasing, whorls; the spire short; Suture 



1 Herzenstein (Op. o. pag. 682) states that it pertains to the 

 White Sea. 



