Vol. 55.] ECTOMARIA AND HORMOTOMA. 263 



and is figured in PI. XXI, figs. 10 & 11 ; it measures 28 mm. in length 

 and 17 mm. in width. 



Dimensions. — The largest British specimen has about five 

 whorls, the apex being broken; its length =19 mm., width of 

 penultimate whorl =8| mm. The smaller shell on the same slab 

 consists of little more than four whorls, which measure 14| mm. in 

 length and 7| mm. in width. 



Locality and Horizon. — Durness Limestone, Sutherland. 

 Salter gives Pauquettes Hapids, Kiver Ottawa ; Ulrich & Scofield 

 also state the occurrence of the var. canadensis^ in the Black River 

 Rocks at the same locality, and say that it is found (more rarely) 

 together with the var. tennessensis'^ in equivalent or somewhat younger 

 strata between jN"ashville and Lebanon (Tenn.). The typical form 

 was obtained in abundance, and the var. nitida ^ rarely, in the upper 

 part of the Trenton Group between Burgin and Danville (Kentucky). 



Eoemotoma(?) gracillima (Salter). (PI. XXI, fig. 12.) 



MurcMsonia gracilis, var. gracillima, J. W. Salter, 1859, Quart. Journ. Geol. 

 Soc. vol. XV, p. 379 & pi. xiii, tigs. 7-8; (pars) R. Etheridge, 1888, ' Foss. Brit. Is.' 

 vol. i (Palaeozoic) p. 113. 



Description. — Shell very elongated, composed of more than 

 twelve gradually increasing whorls, which are convex, but slightly 

 angular near the middle. Surface-ornamentation, band, and aper- 

 ture unknown. Imperforate. 



Remarks. — These shells were referred somewhat doubtfully by 

 Salter to Murchlsonia gracilis, Hall; he observes that they have a 

 smaller spiral angle and more numerous whorls, and he suggests the 

 name gracillima if these differences should be considered of specific 

 value. The only known examples are embedded in the matrix, and 

 are so imperfect that it is impossible to make a satisfactory com- 

 parison w^ith other species ; but, as they certainly appear more 

 slender than Hall's species, I consider it advisable to regard Salter's 

 name as specific instead of merely varietal. 



Dimensions. — There are two specimens in the Museum of Prac- 

 tical Geology, London, the largest of which consists of about twelve 

 whorls, and is refigured in PI. XXI, fig. 12. It measures 37 mm. in 

 length and 9^ mm. in width. The smaller shell has about ten whorls, 

 whose length is 18 mm. Another example is in the British Museum 

 (Nat. Hist.), but it also is merely a section and is not so well 

 preserved as the others ; it measures 36| mm. in length. 



Locality and Horizon. — Durness Limestone, Sutherland. 



Hormotoma(?) dctbta, sp. nov. (PI. XXI, fig. 13.) 



MurcMsonia hellicincta (?), J. W. Salter, 1859, Quart. Journ. Geol. Soc. vol. xv, 

 p. 380 & pi. xiii, tig. 11. 



Description. — Shell elongated, composed of more than three 

 whorls. Whorls flattened, and but slightly convex. Band, orna- 

 mentation, and aperture unknown. 



^ This variety has the band on the middle of the whorl. 



^ Band a little above the middle of the whorl, 



^ This is of larger size, relatively plump form, and has a wider spiral angle. 



