RECENT BRITISH OSTRACODA. 449 



side, oblong, highest in the middle, greatest heiglit equal to less than two-thirds of the 

 length, narrowed and rounded in front, obliquely truncate behind; superior margin 

 strongly arched, inferior rather convex. Outline, as seen from above, broadly ovate, 

 widest behind the middle, extremities pointed ; greatest width equal to more than half 

 the length. End view triangular, equilateral, broad at the apex ; base flat, sides decidedly 

 concave. The shell is obscurely punctate and rugose, and has two more or less strongly 

 marked rounded ribs running from the central portion of thp ala to the extremities of the 

 hinge-margin, and forming, when viewed from above, two large rounded nodes ; the ala 

 itself is more angular than in the preceding species. Animal unknown. 

 Length in. 



Hab. Hebrides and the Mirich, 50-60 fathoms {Mr. J. G. Jeffreys) ; and in shell-sand from Roundstone 

 (Dr. Alcock). 



4. Cytheropteron punctatum, n. sp. (Plate XXXIV. figs. 45-48.) 

 Cytheropteron tricorne, Brady, Brit. Assoc. Report, 1866, p. 208. 



Outline, as seen from the side, very similar to the preceding ; but the posterior margin 

 is broader and more produced above, and the lateral ala much more exserted and ending 

 suddenly, behind the middle, in an acute angle. Outline, as seen from above, rhomboidal, 

 rectangular behind the middle, thence tapering to the acuminate posterior extremity ; or 

 it may be described as consisting of two equilateral triangles applied to each other by 

 their bases, the larger being in front ; greatest width behind the middle and equal to 

 nearly three-fourths of the length. Surface of the shell minutely punctate. 



Length 5V iii- i'" 



Hab. The Minch, 60 fathoms [Rev. A. M. Norman), and oflP Ormeshead {Mr. D. Robertso7i). 



I was at one time disposed to refer this species to a fossil form described by Herr 

 Bornemann under the name Ci/ there tricornis; and in outline the two are, indeed, very 

 similar ; but the fossil species seems to have no punctation of the surface ; and as it differs 

 slightly in other respects, it seems better to keep it distinct. 



5. Cytheropteron mtjlttfortjm (Norman). (Plate XXIX. figs. 38-42.) 



Cythere multifora, Norman, Nat. Hist. Trans. Northumb. & Durh. vol. i. p. 18, pi. vi. figs. 13-16, and Brit. 

 Assoc. Report, 1864, p. 192. 



Atlantic type ? Distribution: Recent — Britain, Ireland. 



Carapace of the female, seen from the side, oblong, rhomboidal, equal in height 

 throughout ; height equal to more than half the length ; ventral ala not very prominent. 

 Extremities irregularly and obtusely rounded, the anterior oblique and forming an obtuse 

 angle at its junction with the dorsum ; superior and inferior margins parallel and nearly 

 straight. Seen from above, the outline is subhexagonal, witli suddenly tapering pointed 

 extremities ; greatest width equal to much more than half the length ; hinge-margins 

 depressed behind the middle so as to form a longitudinal sulcus. End view subtriangular, 

 the three sides convex, apex and base centrally emarginate. Carapace of the male more 

 elongated; sides, as seen from above, parallel. Shell-surface marked with closely set 



VOL. XXVI. 3 p 



