60 ' MES. JA^E Lo:?fGSTArF ois [vol. Ixxiii, 



space. In no instance have I observed a species including indi- 

 viduals with the protoconch greatly elevated and others with it flat. 

 In two species, AcUsina miciila and A. striatissima, I have noted 

 very slight variation. Onh^ two examples of the former are known 

 to me: in one the protoconch adheres closely, in the other it is a 

 little raised, and in one example of A. striatissima (PI. YI, fig. 4) 

 it is flatter than in the type. In some shells one or more of the 

 upper whorls of the spire are unattached, as well as the protoconch : 

 as, for instance, A. aciculata (PL VI, flg. 6). The protoconch is 

 frequently more translucent than, or of a different colour from, 

 the rest of the shell. 



I have previously noted that the Scottish Gasteropoda as a 

 whole are small. There are, however, exceptions to this, for at 

 Craigengien and Strathavon, both near the base of the Lower 

 Limestone Series, larger shells occur, equalling in dimensions indi- 

 viduals of the same species at Settle and Vise. Mr. Peter Macnaii* 

 suggests that this may be the result of the clear- water conditions 

 which prevailed during the deposition of the beds at these localities. 

 It is remarkable that the most minute examples occur at Glencart, 

 Dairy, near the top of the Upj)er Limestone Series ; the pecuhar 

 character of the deposit in which they were found was described 

 by Dr. John Young, and also referred to by me. 



AcUsina and Aclisoides are not associated together in this 

 paper on account of a supposed close relationship, but because, 

 owing to a superficial resemblance, a species of the latter had been 

 mistaken for a member of the former. I have discussed the 

 possible aflinities of Aclisi?ia, and have shown that it beai*s a great 

 likeness to Promathildia Andrese, which genus was then included 

 by some palaeontologists in the family Turritellidae. Koken con- 

 sidered that AcUsina might be the direct forerunner of certain 

 TurriteUce. M. Cossmann has since created the family Mathil- 

 diidse : ^ thus it is now a question Avhether AcUsina should not 

 find a place there in proximity to FromatJiildia. If this were 

 the case, AcUsina would be the most ancient member of the group 

 as now constituted. 



A far greater number of species of AcUsina have been found in 

 Scotland than in any other country. Of the twentj-two recorded 

 only one is peculiar to England, and one, or at most two, to 

 Ireland. The former is the fossil described by Mr. Bolton as 

 Loxonema ashtoneiise from the basement-beds of the Bristol Coal- 

 field. One of the Irish species, A. sulcatula (McCo}'), has not 

 been observed elsewhere ; the other, A. poly(/}/ra (McCoy), is pro- 

 bably conspecific with A. elonr/ata (Fleming), but the holot^'pe is 

 so much embedded in the matrix that it is difficult to be certain 

 of this. 



With regard to the species occurring in Scotland, it may be 



^ ' Essais de Palooconchologie Comi^aree," vol. ix (1912) p. 2, After Avriting 

 the above I received vol. x (1915) of this work, and I observe that on p. 259 

 M. Cossmann does not consider AcUsina to be related to Turriiella, but 

 states that ' I'intermediaire entre Jjoxonema et Mathildia est manifeste.' 



