142 G. LINDSTRÖM, ON TliE SlLUiilAN GA«TK01'0DA AND PTEHOPODA OK GOTLAND. 



Of thu species first included withiii tliis genus ahiiost all havo tlic characteristic 

 featurus of »the oblique prominent thread like strias which cover the surface in all tlie 

 typical species» and as also the etymology of the name iniplies. In spite of such 

 expressly given charaeteristies by the first author låter naturalists have placed within 

 the limits of this genus shells whieh are ornamentcd in a quite different manner, and 

 rather should be regarded as belonging to other genera. Only such shells, in which 

 the ornamental stria' form an angle along the median line of the whorls or near that 

 line coiiformably to the first typical species, should be placed here. 



Michelia of Ad. Ferd. Roemer ^) comprises shells with nearly the same ornamenta- 

 tion as in Loxonema, but with whorls and spire more like those in Trochus or Terebra. 



Species of Loxonema have been foiind in the Silurian and Devonian formations. 



A few have also been found in the Carboniferous limestone, though a great many 

 have been introduced in this genus without showing the distinctive charaeteristies. 

 But of all those described as Loxonema by Laube ^) from the Triassic strata of St. 

 Cassian not a single one can be regarded as appertaining to that genus. 



In the Silurian of Gotland five species have been found, differing from each 

 other in the shape and relative size of the whorls as well as in the position of the 

 insinuation and the character of the angular striaj. 



1. Loxonema sinuosum Sowerby. 



Pl. XV fig. 1-5, 7. 



Terehra? sinuosa 1839. Sowerby in Sil. Syst. 619 tab. 8, fig. 15 (not Salter in Mem. Geol. Survey 



II, I, 357, pl. 14 f. 2, wliioh is = Muich. cingulata His., Loxonema 

 sinuosa Phillips Pal. Foss. Cornwall 99 pl. 38 f. 182 is a Devonian 

 species distinct from the Silurian and bas to be renamed as it is of låter date). 

 Loxonema sinuosum 1848. Bronn Nomenclator, 670. 



1850. D"Orbigny Prodrome I, 29. 

 1854. Morris Catal. Brit. Foss. Ed. 2, 255. 

 1859. Salter Siluria 3 Bd., 549 tab. 24 f. 3. 

 1873. Id. Catal. Cambr. Foss., 172. 

 Holopella {obsoletw Sow. aff.) 1867. Lindström Nomina, 23. 



Shell elongate, turriculate, with eight whorls, which are transverse, broader than 

 high, ventricose, constricted in a narrow belt close at the suture and the lowest edge 

 of the whorl hiding and covering the suture. Suture crossing the axis of the shell 

 in a very acute angle. The surface is covered by very fine, elevated lines, which are 

 bent in a nearly rectangular curve, along a line somewhat below the transverse median 

 axis of the whorl corresponding with the position of the obtuse indentation of the 

 aperture. The striee are finest on the body whorl, being more and more coarse and 

 changed into elevated, angular ridges on the older whorls. The aperture is ovate, 

 the columellar lip having besides it only a narrow, umbilical fissure open, which is 



') Palceontographica Bd. 3, p. 73. 



-) Denkschriften der Ak. d. Wiss. zu Wien 1868 Zweite Abth., p. 60. 



