472 MR. G. S. BRADY'S MONOGRAPH OF 



Probably this is not an uncommon genus ; but the extreme minuteness of the animal 



rrnders it very liable to be overlooked. 

 For the anatomical description given above I am indebted to G. O. Saw's work. The 



- line 



author remarks that the motions of the animal much resemble those of 



species of Chydoms ; it is exceedingly active, having no less than ten limbs adapted for 



swimming 



2. Polycope (?) dentata, n. sp. (Plate XXXV. figs. 58-59.) 



Carapace, as seen from the side, subcircular, highest in the middle ; greatest height 

 qual to fully three-fourths of the length. Anterior margin notched above the middle, 



notch broad and shallow ; inferior obliquely arched, moi 



front than behind 



superior margin of the left valve simply and obliquely arched, the convexity being 

 greatest behind, that of the right valve surrounded by a narrow fillet produced in front 

 into two large, broad, and bluntly pointed teeth which are directed forwards, behind 

 which it is at intervals obtusely angulated, so as to form four sides of a polygon, and 

 ends suddenly in a slightly exserted angular tooth above the middle of the posterior 



Outline, as seen from above, compressed ovate ; sulcate along the hinge-line. 

 Shell thin and fragile; surface closely, minutely, and uniformly punctate ; colour yel- 



marg 



lowish. Animal unknown. 

 Length -^ in. 



Hab. Shetland (Rev. A. M. Norman). 



It may perhaps be doubtful whether this very remarkable and beautiful little species 

 is rightly referred to the genus Polycope : it is at any rate very nearly allied to that 

 genus ; but as one specimen only has been found, the anatomical details of the animal 

 cannot at present be investigated. 



Section IV. PLATYCOPA. 



Fam. CYTHERELLID.E. 



"Valves unequal, very thick and calcareous, not notched in front. Antennae very 

 large, the upper many-jointed and geniculate at the base ; lower broad and flattened, 

 two-branched, like the feet of the Copepoda. Mandibles very small, with a large pec- 

 tinato-setose palp. Three pairs of hinder limbs, scarcely pediform ; the two anterior pairs 

 branchial, the others rudimentary. Abdomen terminating in two very small, narrow, 

 and spiniferous laminae. Ova and embryos borne beneath the shell of the female." 



Genus Cytherella, Bosquet. 



" Valves elongated, flattened, thick, and hard, very unequal ; the right much larger 

 than the left, and overlapping throughout the whole circumference, presenting round 

 the entire inner margin a distinct groove into which the valve of the opposite side is 

 received. Upper antennas very large, shortly setose or spiniferous, seven-jointed, the 







