Vol. 54.] MISS J. DOlsTALD ON THE GENTJS ACLISINA. 55 



neither describes it more fully nor gives a new figure. The original 

 figure does not show the arrangement of the ornamenting striae, 

 and upon examination of the actual specimens I found that several 

 distinct spirally-striated shells had been included under one specific 

 name. There are fragments of the form I described as A. elowjata^ 

 Pleming, one of which consists of four and a half whorls, the 

 upper part of the spire being broken, its length =1| mm., width 

 = about I mm. To prevent confusion I have thought it ex- 

 pedient to retain this shell as the type of A. elongata. Besides 

 this species there are representatives of shells I have described as 

 A. costatula, A. attenuata, A. jjulchra var. tenuis, as well as a 

 specimen which I regard as a variety of A. elongata. 



The type of A. elongata has five or six raised threads on the 

 lower convex part of the whorl, with equal spaces between them, 

 and two threads on the upper flattened part, with wide spaces 

 between them, one a short distance above the lower threads, and 

 the other immediately below the suture. One or both of these upper 

 threads is frequently absent. It is worthy of remark that this 

 lack of ornament on the upper part of the whorl is not a peculiarity 

 of this species alone, but it may be frequently observed in others. 

 It is impossible to say whether this portion of the ornamentation 

 was not originally present, or whether its absence arises from wear 

 either in the natural state or subsequent to fossilization. 



In beds where this species is abundant there is a certain amount 

 of variation from the type in the strength, disposition, and number 

 of the ornamenting threads, and I here note under distinct names 

 two well-marked varieties. A fragment of one (PI. Ill, fig. 9) is 

 preserved in the Ure Collection ; six whorls are intact and have a 

 length of 2 mm., width of about 1 mm. There are six or seven 

 threads on the convex part of the whorl, rather finer than those on 

 the type, and with narrower spaces between, with the exception of 

 the uppermost space, which is wider and is about equal to that next 

 above on the flat part of the whorl ; in other respects this variety 

 is similar to the type. I would suggest for it the name varians. 



The other variety has the threads separated by wider spaces 

 above and below, with a band of two or three fine threads separated 

 by narrower spaces between. Otherwise it agrees with the type. 

 It may be called cingulata (PL III, figs. 10 & 10 a). 



A small specimen (PL III, figs. 7 a,h&c) in Mr. John Smith's 

 collection from Crawfield has the protoconch entire ; the whole shell 

 is contorted, and the apex is much worn. The protoconch is more 

 or less orbicular, smooth, and detached from the highest whorl of 

 the spine on the umbilical region. Its junction with tlie conch is 

 indicated by a faint rib, but the commencement of the spiral threads 

 is not seen. 



The spiral angle also varies to some extent. 



Loxonema polygyra, M'Coy (PL III, fig. 11), is probably identical 

 with this species and more nearly agrees with the type than the 

 varieties. There is but one specimen in the Museum of Science 

 and Art, Dublin. It is partly embedded in the matrix of shale, 



