360 VENERIUM. 



are more strongly pectinated on the inner than on the outer 

 surface : palps very small for the size of the animal, triangular, 

 and striated like the branchial laminae : foot large, white, mus- 

 cular, lanceolate, bent, and furnished with a byssal groove. 



Shell having a general resemblance to T. pullastra, but 

 distinguishable by the following characters. It is usually not so 

 convex, and less broad (or shorter from one end to the other) : 

 sculpture much coarser, the longitudinal striae being quite as 

 strong as the transverse ribs and often more raised ; the surface 

 is thus reticulated, and marked (especially on the posterior 

 side) by rows of tubercles : colour of a more sombre and 

 uniform hue, mostly yellowish and variegated with rays and 

 zigzag streaks or spots of dark or light brown : dorsal margin 

 more straight and the posterior slope decidedly truncate. 

 L. 1-75. B. 2. 



Yar. quadrangula. Shell smaller, square-shaped, and more 

 convex. 



Habitat : Muddy gravel and sand at low- water mark, 

 with T. pullastra, on the shores of our southern and 

 western counties, Wales, and Ireland. Cheshire coast 

 (Hall) ; Scarborough (Bean) ; Northumberland and 

 Durham (Alder) ; Berwick (Johnston and Maclaurin) ; 

 Clyde district (Eyton); Oban (J. G. J.); Sound of 

 Iona (Bedford) ; Skye (Forbes) ; Aberdeen (Macgil- 

 livray) ; Shetland (Forbes and M 'Andrew). Var. 

 Cork (Humphreys) ; Bantry Bay (Barlee). This spe- 

 cies is subfossil in the Loch of Spynie, and in the 

 " Kjokkenmoddings," Morayshire (Gordon) : fossil in 

 the Scotch glacial beds (Smith) ; Belfast " alluvial " 

 deposit (Hyndman and Grainger) ; Sussex tertiaries 

 (God win- Austen). It also occurs with shells of Arctic 

 species in the newer pliocene strata of Bohuslan (Malm), 

 Uddevalla (J. G. J.), and Christiania (Sars) ; and with 

 shells of southern species in the Sicilian tertiaries (Phi- 

 lippi). It has not been noticed in a living or recent 

 state by any writer on the northern or Scandinavian 



