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 fiexuous 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 
gravel, 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 Eobertson, Ann. and 
Mag. Nat. Hist., ser. iv., vol. xi. p. 66 (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 ; bottom 
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. 
