1873.] MR. R. B. WATSON ON MADEIRAN MOLLUSKS. 367 



r 



Hab. Gorgulho, shore ; Santa Cruz, shore ; Selvagens, shore ; 

 Pontade Sao Lourenco, shore to 45 fathoms ; Piedade (Canical), 15 

 to 35 fathoms ; Funchal Bay, up to 50 fathoms ; Porto Santo, up to 

 50 fathoms. 



My specimens from the Selvagens, given me by the Baron de 

 Paiva, are very large and strongly tubercled from the strength of 

 the longitudinal and spiral threads. 



I strongly suspect that this is the same species as Signor Manzoni's 

 R. calathus from the Canaries and Madeira. That certainly has 

 teeth within the lip and is somewhat stumpier in form ; but these 

 are both variable characters ; and in spite of the somewhat rubbed 

 and bleached condition of the specimens (from Tenerife) of Manzoni's 

 species, which I owe to the kindness of Mr. M'Andrew, I have 

 recognized the characteristic markings on the embryonic shell as 

 identical with those of my species. 



That this species, at least, is distinct from R. calathus is a view 

 in which I am supported by the opinion both of Mr. Gwyn Jeffreys 

 and of the Baron Schwartz v. Mohrenstern. The two species have 

 certainly some points of superficial resemblance, but differ in form, 

 in texture, in colour, in threading both longitudinal and spiral, in 

 the shape, make, and colour of the pillar, whole shape of mouth, 

 constitution of outer-lip margin, and in markings of embryonic 

 tip (?). 



I have named the species after my friend Mr. Thomas Leacock, 

 who has done much for the study of the Madeiran land-mollusks. 



Rissoa cancellata, da Costa. (Plate XXXIV. fig. 2.) 



In M'Andrew's list. 



Hab. Gorgulho, shore ; Ribeiro secco, 10 fathoms; Santa Cruz, 

 10 to 15 fathoms ; Machico, 10 to 15 fathoms ; Piedade (Canical), 

 15 to 35 fathoms ; Ponta de Sao Lourenco, 25 to 45 fathoms ; Porto 

 da Cruz, 50 fathoms ; Porto Santo, 50 fathoms ; Funchal Bay, 

 50 fathoms. 



A European, Mediterranean, and Canary species. 



The Madeiran form of this shell is smaller than the British, and 

 the whorls are more angulated. The teeth within the mouth are 

 fewer by a half than the number given for them by Mr. Gwyn 

 Jeffreys (vol. iv. p. 9, Brit. Conchology) ; but this is a feature of 

 very little specific value. 



jla Rissoa atjrantiaca, Watson. (Plate XXXIV. fig. 3.) 



- s - ; Shell oblong, thick, not transparent, a little glossy, tubercled, 

 rising in steps. 



Sculpture, longitudinal ribs, on body-whorl 18 to 20, gently 

 rounded, disappearing on base ; diminishing in number upwards on 

 the whorls, and absent on the embryonic whorl ; each is about 

 twice as broad as the interval between them. 



