part 2] ACLisiyA and aclisoide^. 59 



4. Supple MENTAEY Notes on Aclisina De KojS'ixck and Aclt- 



soiDE^^ Donald, with Descriptions of New Species. Bj 



Jane Longstaef (jiee Donald), F.L.S. (Communicated 



by Dr. a. B. Longstaef, M.A., F.a.S. Read May 2nd, 



. 1917.) 



[Plates V & VI.] 



In 1898 I commmiicated a paper to this Societ}' on the genus 

 Aclisina and on Aclisoides, a new section or subgenus of Murchi- 

 sonia. Since that date I have had the opportunity of studying 

 a larger number of specimens, which has not only enabled me to 

 learn more about the species then described, but also to add to 

 their number. 



Fifteen species of Aclisina with several varieties, and a single 

 species of Aclisoides with one variety, were dealt with in 1898. I 

 am. now referring seven more species to the former, six of which have 

 not been previously noted, and am regarding the form considered 

 a variety of the latter as a distinct species. Thus we have a total 

 of twenty-two possible species of Aclisina and two of Aclisoides. 

 In addition to these there are in the Sedgwick Museum, Cambridge, 

 three small shells resembling Aclisina, one from Poolvash, the 

 others from Settle, all too much embedded in the matrix to be 

 accm-ately determined. 



The numbers given can only be regarded as approximate, for 

 paucit}^ of specimens and defects in the manner of preservation 

 sometimes render the definition of genera and species difficult. It 

 is, therefore, possible that some shells at present considered as 

 distinct species may afterwards prove to be varieties only, while 

 others now grouped together may need to be separated. 



In the previous paper no holotypes were selected. I am now 

 supplying the omission, and also stating in which collections they 

 are deposited. 



Although I have already remarked on the beautiful state of 

 preservation of many of the Scottish specimens, it ma}^ not be 

 amiss to draw attention to it again. No less than thirteen species 

 of Aclisina and one of Aclisoides have the protoconch well pre- 

 served. In the latter it is attached to the post-embryonic whorl 

 and simply coiled on the same plane, and thus in no wise peculiar. 

 But in Aclisina it is markedly so, being more or less irregular. 

 In six species the protoconch stands up, forming a Avide angle with 

 the post-embr3^onic whorl ; in four it is not so much raised, but is 

 oblique and overhangs the spire ; in the remaining three it is 

 wholly attached, forming a broad flat apex. 



The material at hand is not sufficient to show to how great an 



extent variation in the character of the protoconch of a species mjjiif^*^ • «'T*^^ 

 take place, either in the same beds, or in those separated by tuif^^^ "^tti 



Q. J. G. S. No. 290. G A>^ 



r JAN 10 191' 



