50 MISS J. DONALD ON THE GENUS ACLISINA. [Feb. 1 898, 



a great likeness to some Mesozoic forms, such as the Triassic Turri- 

 tella ])cedopsis, Kittl,^ T. Bernardi^ Kittl,^ and the Liassic T. 

 [^Mesalia] Guembeli, von Ammon,^ in form, ornamentation, and in the 

 structure of the outer lip. 



The character of the protoconch greatly resembles that of Proma- 

 thildia, Andreae, as represented b}'' Koken "^ and Kittl/ from the 

 St. Cassian Beds, which does not appear to be heterostrophe like 

 that of Mathilda, Semp., but merely irregular and partially de- 

 tached from the conch. The form of the outer lip is similar, but 

 the aperture of Aclisina is not channelled below like that ot 

 Promathildia. 



A consideration of the above-mentioned points of comparison 

 must show how difficult it is to decide in which family this genus 

 should be classed. De Koninck refers it to the Turbinidae, with 

 the members of which, however, it does not appear to me to 

 have much in common. In his 'Handb. der Palaont.' vol. ii (1881- 

 85) p. 188, Zittel also places it in the Turbinidae ; but in his 

 later work, ' Grundziige der Palaont.' 1895, p. 338, he includes it 

 in the ScalariidsD. Fischer ('Man. Conch.' 1885, p. 778), Tryon 

 (' Man. of Conch.' vol. viii, p. 53), and Whidborne (' Monogr. Dev. 

 Fauna,' Pal. Soc. vol. iii, pt. i, 1896, p. 152) refer it to this last- 

 named family, and Fischer considers it identical with Holopella ; 

 but it differs in being ornamented by spiral striae, instead of being 

 smooth or having longitudinal ribs. S. A. Miller (Geol. Surv. 

 Indiana, l7th Ann. Eep. 1891, p. 695) gives it a place in the 

 Turritellidae, where it seems advisable to let it remain for the 

 present, as it appears to combine characteristics both of the Turri- 

 tellce of the older rocks and also of PromatJiildia. There is a 

 difference of opinion as to the position of the latter genus ; some 

 place it in the Turritellidae, while others class it in the Cerithiidae, 

 and others again in the Pyramidellidae. Aclisina differs from the 

 Cerithiidae in not having a channelled aperture. It agrees with 

 the Pyramidellidae, as defined by Zittel,^ in the outer lip being 

 sigmoidal and in possessing an irregular protoconch. 



Range. — In the present state of our knowledge it is almost impos- 

 sible to ascertain the exact range in time and space of Aclisina, for 

 the distinction between the members of the genus and other small 

 spirally- striated shells has not hitherto been noted. Koken (' Die 

 Leitfossilien,' 1896, p. HI) states its range as being from the 

 Carboniferous to the Permian. He considers the American forms 



^ ' Die Gastr. der Schichten von St. Cassian der siidalpinen Trias,' Annal. 

 k.-k. naturhist. Hofmus. vol. vii (1892) p. 55 & pi. vi, fig. 1. 



^ ' Die triadischen Gastr. der Marmolata u. verwandter Fundstellen in den 

 weissen Eiffkalken Siidtirols,' Jahrb. k.-k, geol. Reichsanst. vol. xliv (1894) 

 p. 149 & pi. vi, fig. 24. 



^ ' Gastr. aus dem Plattenkalk,' Abb. zool. min. Ver. Regensburg, vol. xi 

 (1878) p. 59 & pi. i, figs. 12 a-e. 



^ * Ueber die Entwickelung der Gastr. vom Cambrium bis zur Trias,' Neues 

 Jahrb. Beilage-Band vi (1889) p. 459, fig. 25. 



^ ' Die Gastr. der Schichten von St. Cassian der siidalpinen Trias,' Anual. 

 k.-k. naturhist. Hofmus. vol. ix (1894) p. 224 & pi. ix, fig. 36. 



« ' Grundziige der Palaont.' 1895, p. 340. 



