﻿224 DEVONIAN FAUNA. 



falls in the centre of the aperture. Kayser unites with his shell several species 

 of F. A. Romer and Giebel, all differing from the present shell in this particular. 



VI. Family. — Scalaiudj:, Chenu. 



1. Genus. — Holopella, M'Coy, 1852. 



The shells of this genus are very elevated, with very numerous narrow whorls, 

 and with very fine longitudinal and also sometimes spiral stria?. The surface has 

 often a polished or glossy appearance. It extends from the Silurian to the Trias. 



1. Holopella tenuireticulata, n. sp. PL XVIII, figs. 9, 9 a, 9 b. 



Description. — Shell of moderate size, very elongate, spiral, tapering regularly, 

 many-whorled. Sutural angle varying. Suture small, shallow, rather wide. 

 "Whorls increasing regularly, short, being about half their diameter in height, 

 slightly convex, sloping flatly from the upper suture, and becoming suddenly 

 more convex at their posterior end so as to slightly overhang the lower suture ; 

 ornamented by multitudinous, fine, sharp, rather irregular striae, sloping straightly 

 and obliquely backwards from the upper suture over the greatest part of the 

 whorl, but curving rather more forwards in its lower region, and imbricated by 

 equally numerous, rounded, spiral threads, so as to form a very fine lozenge- 

 shaped reticulation. Body-whorl small, curving suddenly in its lower part, and 

 continued flatly and obliquely inwards to form the base, which is marked only 

 by spiral threads, as the perpendicular lines have in that part almost entirely 

 disappeared. Mouth ovate. Columella straight. Shell-structure thin. 



Size. — Height (of three and a half whorls) 30 mm., width 12 mm. 



Locality. — Wolborough. A single example is in Mr. Vicary's Collection. 



Remarks. — This shell appears to be distinguished by the exceeding fineness of 

 its ornamentation, by its very elongate form, and by its narrow whorls. The 

 sharp perpendicular lines are broken into a series of frills by the imbrication of 

 the spiral threads. The spire appears to taper regularly as far as is shown by 

 the portion remaining in Mr. Vicary's specimen, and if this were continued 

 throughout it would indicate a shell between 70 and 80 mm. high, but most 

 probably the rate of tapering increased apically, so that the shell would be 

 somewhat shorter. The sutural angle is very variable, so that the lines of the 



