1873.] MR. R. B. WATSON ON MA3KIRAN MOLLUSKS. 3()J 



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

 15 fathoms; Machico, shore to 15 fathoms; Piedade (Cauical), 15 

 to 35 fathoms ; Ponta de Sao Lourenco, 25 to 45 fathoms ; Funchal 

 Bay, up to 50 fathoms ; Porto Saato, up to 50 fathoms ; Teueriffe 

 {fide Jeffreys, Brit. Cou. vol. iv. p. 38). 



A coralline-crag, Arctic, Siberian, European, Mediterranean, 

 Canary, and East North-American {fide J. G. Jeffreys, Ann. & 

 Mag. Nat. Hist. 1872) species. 



Is this Madeira species really the R. striata of Adams 1 There is 

 much to justify its elevation into a distinct species. It can be un- 

 failingly distinguished by the strong basal threads. The difference 

 between them, however, I have sought to mark by calling this var. 

 lirata. 



There is a further variety existing equally among Madeiran and 

 British forms of this species, which might be indicated by the var. 

 called Candida by Brown ; only this var. is not " devoid of the 

 longitudinal ribs " as Candida is. It is more cylindrical, narrower, 

 with whorls more fully rounded, and with a broader second whorl, 

 and with a more spherical tip ; compared with this the typical form 

 is more conical, with an outline less interrupted by the sutures, 

 somewhat shorter in proportion to breadth, and narrowing upwards 

 more equally to a small rounded but depressed apex. 



As in almost all species, a larger and a smaller form are also 

 found. 



I owe my Selvagens specimens to the kindness of the Baron de 

 Paiva. 



Rissoa cost ata, Adams. (Plate XXXIV. fig. 5.) 



Not in M'Andrew's list. 



Gorgulho, shore ; Selvagens, shore ; Santa Cruz, shore to 1 5 

 fathoms ; Machico, shore to 15 fathoms ; Piedade (Canigal), 15 to 

 35 fathoms ; Ponta de S. Lourenco, 25 to 45 fathoms ; Funchal Bay, 

 up to 50 fathoms ; Porto Santo, up to 50 fathoms; Teneriffe, fide 

 M 'Andrew. 



A European, Baltic, Mediterranean, and Canary species. 



The embryonic whorl of this shell is not "quite smooth," but 

 carries distinctly the spiral striae. 



The Madeiran form, like that {fide Jeffreys, B. Con. iv. p. 23) 

 found at Spezzia and Tenerife, is very small. 



I owe my Selvagens specimens to the Baron de Paiva. 



Rissoa crispa, Watson. (Plate XXXIV. fig. 6.) 



Shell conic-oval, whorls rising above each other in steps, solid, 

 translucent, somewhat glossy. 



Sculpture: longitudinal ribs about 12, distant, narrow, ridge-like, 

 not flexuous, but strongly bent from left to right ; these become 

 rather fewer upwards, and disappear on the first and second whorls ; 

 they lap up on the preceding whorls (without adhering to them), 

 and nearly conceal the suture. On the body they hardly stretch 

 below the periphery, being cut off in a broadish furrow, which runs 



Proc. Zool. Soc— 1873, No. XXIV. 24 



