of the Fishery Board for Scotland. 323 



ventral margins nearly straight, the former is slightly convex towards the 

 anterior extremity ; anterior margin evenly rounded, posterior extremity 

 with a short beak situated about the middle, its termination narrow, 

 truncate. Seen from above, ovate, slightly constricted in front, where the 

 valves meet. At the posterior end, the middle is bluntly mucronate, and 

 the sides are produced to an acute angle, so as to impart to it a somewhat 

 tridentate appearance ; dorsal ridge prominent, where it bends downwards 

 in front. Surface sculptured with flexuous longitudinal riblets, crossed by 

 a few indistinct ones arranged irregularly. Length, *5 mm. ; breadth, 

 £ length ; height, fully J the length. 



Habitat. — Off St Monance, in 12 to 14 fathoms, bottom sand and 

 travel, rare. 



This species somewhat resembles Cytherura acuticostata, but differs in 

 being not so stout, and in having the valves produced backwards, so that 

 the posterior extremity of the shell has a tridentate form. 



Cytherura mucronata, n. s. (PI. XII. figs. 3, 5). 



Shell seen from the side, elongate, narrow ; height about equal at both 

 ends, length two and a half times the height ; dorsal margin nearly straight, 

 ventral margin slightly and evenly concave, posterior end much produced 

 and wedge-shaped, forming a ' beak,' which is situated below the middle ; 

 anterior margin broadly rounded, somewhat produced in the middle. 

 Seen from above, oval, with the ends acuminate ; the margin at each end, 

 especially the anterior margin, is produced, so as to form a distinct 

 ' mucro.' The surface is marked with indistinct raised lines, which are 

 somewhat irregularly distributed; the breadth is equal to the height; 

 length, *33 mm. 



Habitat. — Off St Monance, not very rare. 



Cytherura simplex, Brady and Norman. 



Cytherura simpex (name only), Brady and Robertson, Ann. and 



Mag. Nat. Hist., ser. iv., vol. xi. p. 6G (1872). 

 Cytherura sarsii ("local variety"), idem ibidem, vol. xiii. p. 117, 



pi. iv. figs. 6, 7 (1874). 

 Cytherura simplex, Brady and Norman, op. cit., p. 200, pi. xviii. 



figs. 1, 2. 



Habitat. — Off St Monance, frequent, depth 12 to 15 fathoms ; bottum 

 clean sand, part gravel. Viewed laterally, the shell of this species differs 

 somewhat from the usual form of Cytherura, which has a more or less 

 distinct 'beak' at the posterior end, whereas this has no posterior beak. 

 New to the east of Scotland. 



Cytherura fulva, Brady and Robertson. 



Cytherura fulva, Brady and Robertson, Ann. and Mag. Nat. Hist., 



ser. iv., vol. xiii. p. 116, pi. iv. figs. 1-5 (1874). 

 Cytherura fulva, Brady and Norman, op. cit., p, 205, pi. xix. figs. 



9-11. 



Habitat. — Largo Bay and other parts of the Estuary, but not common, 

 New to the east of Scotland. 



Cytheropteron punctatum, Brady. 



Cytheropteron punctatum, Brady, op. cit., p. 449, pi. xxxiv. figs. 



45-48. 

 Cytheropteron punctatum, Brady and Norman, op. cit., p. 211. 



Habitat. — Off St Monance, rather rare. I do not find any previous 

 record of this species for the east of Scotland. 



