46 MISS J. DONALB ON THE GENUS ACLISINA. [Feb. 1 898 



always give a correct idea of the species. The lines of growth, 

 which are represented only in pi. xxxiii, fig. 42, are also different, 

 as they come more directly down the whorl than on the specimens 

 which I have observed. On these the lines of growth curve backward 

 and form a sinus situated on the space occupied by the band of 

 three threads referred to above, and they curve forward again 

 below in a manner similar to Murchisonia. The ornamenting 

 threads agree with the description of De Xoninck in being about 

 ten in number, and in varying in strength, though this variation in 

 strength is not quite so regular either on the same individual or on 

 different ones as De Koninck describes. In spite of the discrepancy 

 pointed out between the description and figures and the actual 

 .character of the specimens referred to, it seems as if these latter 

 must be considered as typical of the species MurcJiisonia [Adisina] 

 Mriatida^ De Kon., as they are the only specimens which in any degree 

 tally with the representations of De Koninck. jVIore especially does 

 this appear the proper course to be taken when it is noted that, 

 besides the specimen in the Brussels Museum marked as the type, 

 the two shells in the British Museum (Nat. Hist.) are so named in 

 De Koninck's own handwriting. 



This species cannot, however, be regarded as the type of Adisina, 

 as it possesses a sinus in the outer lip, and does not therefore agree 

 with the description of that genus ; but it must be retained among 

 the Murchisonice, where De Koninck first placed it. 



The two other species referred to this genus are Adisina jpuldira, 

 De Kon., pi. vii, figs. 26-28, and A. nana, pi. vii, figs. 29 & 30. 

 The type of the latter in the Brussels Museum is very small, and 

 is distorted by pressure, but there are good specimens of it in the 

 Liege Museum from the same locality, and also one in the collection 

 of M. le Chanoine de Dorlodot from Tournai. One from the Liege 

 Museum has the lines of growth well preserved ; they are sinuated 

 on the earlier whorls of the spire, and on the body- whorl of the 

 adult this sinuation appears to become deeper, so as to indicate a 

 shallow notch in the outer lip, but not a slit as in the outer lip of 

 Murchisonia. This notch is situated higher on the whorl than the 

 sinus of M. striatula, and the lines of growth do not make so great 

 a sweep either backward or forward as in that species. The 

 notch of A. nana, like the sinus of M. striatula, occupies the space 

 between two of the ornamenting threads, and there is sometimes a 

 fine thread down the middle. 



This shell also diverges from the generic description of Adisina 

 in the form of the outer lip, but it cannot be referred to Murdiisonia^ 

 not having either the characteristic slit in the outer lip or the band 

 of that genus. I would suggest the name Micrentoma for the genus, 

 with Adisina nana, De Kon., as the type. 



A. jpuWhra displays, however, a character very different from 

 M. striatula and Micrentoma [Adisina'] nana. A specimen in the 

 collection of M. le Chanoine de Dorlodot shows the form of the 

 outer lip better than De Koninck's type in the Brussels Museum, or 

 the other two specimens associated with it. Here the outer lip 



