BY H. LEIGHTOX KESTEVEN. 631 



specimens, all exactly similar, of the form locally kuown as R. 

 plana, Q. ct G., nine were males and the remainder females. 



Tryon's reference (24) of PlesiotrocJnis, Fischer (3), and Limno- 

 trochtcs, Smith (20)^ to Risella as subgenera was altogether wide 

 of the mark. Fischer's reference (4, p. 687) of the former to the 

 Planaxidte is much more likely to be correct. The systematic 

 position of the latter has lately been ably discussed by Lettice 

 Digby (2). 



Risellopsis, Kesteven (9), is included here almost entirely on 

 conchological characters, nothing beyond the operculum and 

 dentition being known of its anatomy; amd on these it might 

 equally be referred to the Littorinidse. 



The genus appeals to the writer as a perpetuation of the 

 immature condition of Risella (vide fig. 11, pi. xxx.). 



MODULID.E. 



To this family, hitherto having but one genus — Modulus — I 

 propose to add Echiiiella, Swainson, and Peasiella, Nevill (14). 

 Echinellawd.^ proposed by Swainson (22) in 1840 for the reception 

 of two species — Tl. granidata, Swains., and E. coronaria, Lamk. 

 The former of these is apparently a nomen nuduvi, and has never, 

 so far as I can ascertain, been identified. The latter has, there- 

 fore, been regarded as the type. Tryon (25, p. 231), sub voce 

 Tectarius says : — " I am also compelled to unite with this group, 

 as synonyms, Nina, Gray, 1850, and Echinella, Swainson, 1840, 

 their characters being very variable, and shading into those of 

 the type." Fischer (4) treated the genus as valid, placing it after 

 Tectarius, in the Littorinid^e. He thus describes it : — " Coquille 

 imperforee, granuleuse, epaisse; spire elevee, pyramidale; overture 

 striee a I'interieure; base de le columelle inuni d\ine dent; 

 opercule poly gyre, d nucleus central.^'' The italics are mine. 



In arriving at the above conclusion, Trj^on could only have 

 studied the tooth on the base of the columella as the recognition 

 mark of Echinella. This he would have found unreliable, since 

 it is slightly developed in Tectarius pagodas, Linn. The more 

 important character of the multispiral operculum was, in all 



