46 JOURNAL OF CONCHOLOGY, VOL. 15, NO. 2, APRIL. 1916. 



penultimate whorl; R. caticellaia has always three."^ But the male 

 or dwarf form of R. cancellata almost invariably has two riblets only. 



R, calathus F. & H. — Torbay ; Benbecula. Jeffreys' figure 

 should be more oblong. 



R. hispidula Monts.(=:7?. clathrata Phil., II., pp. 223 and 227, t. 

 28, fig. 20, Naples). — This species is new to Britain. Dredged off the 

 Menavawr, Scilly Islands, in 40 fathoms, two specimens only, of the 

 male or dwarf form, but I suspect other specimens have been over- 

 looked. It is not uncommon in the Mediterranean. I have previously 

 pointed out" how difficult it is to find a line of demarcation between 

 R. calatJms and R. reticulata^ but this species tends still further to 

 obscure the boundaries of the three, in consequence of their extreme 

 variations in size and sculpture. The R. clathrata of Philippi has been 

 mistaken by various writers for R. reticulata, R. calathus, and R. 

 zetlandica, and the extra-British records of all four species, therefore, 

 require revision and verification. As an instance of this want of 

 identity, I may pomt out that Gwyn Jeffreys, in his report of the 

 'Porcupine' Expedition, not only omits R^^..^ hispidula altogether 

 (though it occurred in many of the dredgings, sSfoetimes abundantly), 

 but in his records therein of R. calathus and R/. reticulata I am able 

 to say, from my own knowledge, that most of them arc referable to 

 R. hispidula. R. zetlaiidica may very well be eliminated from the 

 group we are considering, as no one need now mistake that species, 

 but the other three seem hopelessly involved when examining large 

 numbers, notwithstanding that individual examples may be placed 

 side by side which indicate differences, and appear as distinct as any 

 other three species of Rissoa. It is, again, one of those cases in which 

 neither description nor figures seem to be of ready help, but the 

 student must of necessity go patiently through series of each from 

 different places. Now, R. hispidula comes between R. calathus and 

 R. reticulata, the finer-sculptured forms approximating to R. reti- 

 culata, and the coarser to R. calathus, while all the variations of form 

 and size presented by the two latter are represented in this and even 

 extended; but, generally speaking, R. reticulata is oblong, the spiral 

 sculpture prevails over the longitudinal, and the penultimate whorl 

 has six rows of spirals ; R. calathus is oval, the longitudinals prevail, 

 and the penultimate whorl has four spirals ; while R. hispidula is 

 conical, the spirals and longitudinals are equalised, and the spiral riblets 

 on the penult vary from six to three, very rarely two. The difficulty of 

 separation is especially great in the dwarf or male forms. 



R. reticulata var. marice. d'Orb., of which I have a specimen 



1 Monterosato : Nomenclatura, p. 64. 



2 Journ. of Conch., 189S, vol. i.x., pp. 125-127. 



