Vol. 54.] MISS J. DOJTALD ON THE GENUS ACLTSINA. 61 



whorls. Ornamentation consisting of numerous spiral threads and 

 grooves ; on the five or six earlier whorls the threads are fewer and 

 stronger, but on the lower two-thirds of the later whorls they are 

 finer and more numerous, being from ten to twelve in number ; the 

 grooves also vary in width, a variation which gives the whorl a 

 banded appearance. Sutures deep. Base convex. 



Resemblances. — In my paper in Trans. Cumberl. & Westmorl. Assoc, 

 I confounded this shell with A. striatula, De Kon., the type of which 

 I had not then seen, but I am now convinced that this is quite a 

 distinct form. Young specimens might be taken for A. elongata from 

 the resemblance in the arrangement and number of the threads ; but 

 the fine banded appearance of the later whorls is very distinctive ; 

 the whorls also appear to be more convex. Nevertheless this may 

 possibly be a variety of that very variable species, especially as there 

 are forms which appear intermediate between the var. cingulata and 

 A. tenuistriata. It is distinguished from A. grantonensis by its 

 more evenly convex whorls and by the fine threads not being sa 

 regularly intercalated between the coarser ones. The apex of all 

 the specimens that I have seen is broken. 



Locality and Horizon. — The specimen figured (PI. lY, fig. 10) is- 

 from the Lower Carboniferous rocks at Pentou ; it has ten whorls 

 preserved, and its length=5 mm. ; its width = 1| mm. One other 

 example occurs in the Lower Limestone Series {cF) at Law, Dairy. 

 It is in the collection of Mr. Bennie, and it possesses eight whorls^ 

 whose length =2 mm. 



AcLisiNA QUADPvATA, sp. nov. (PL IV, figs. 11, 11 a, 12, 12 a & h.) 



Description. — Shell elongated, slender, composed of thirteen whorls. 

 Whorls increasing gradually, moderately convex, slightly quadrate in 

 form : the lower whorls are rather high in proportion to the width, 

 and the upper are wider. Ornamentation consisting of numerous 

 fine threads and grooves, about fifteen in number on the penultimate- 

 whorl, with several more on the base. Two or three grooves 

 near, or immediately below, the middle of the whorl are wider than 

 the others ; the threads and grooves are more equal and less 

 numerous on the higher part of the spire. Sutures deep, moderately 

 oblique. Aperture longer than wide. Columella slightly thickened, 

 rather oblique. 



BemarJcs. — The surface of the upper part of the whorl is not well 

 preserved, and the threads on it are faint or absent altogether. 



I know of only two specimens of this species. The finest (PI. IV, 

 fig. 11) is in Mr. Bennie's collection ; it consists of thirteen whorls, 

 whose length = 5| mm., width = l^ mm. The other belongs to- 

 Mr. Smith and possesses only nine and a half whorls, both apex 

 and base being broken : its length = 4| mm. 



A more slender form, which appears to be a variety of this species,- 

 occurs in the same locality and is more abundant. It is distin- 

 guished by being less compactly coiled, by having the whorls more- 

 exsert and consequently higher in proportion to the width. A^ 



