of ilie North A tlantic and of North- Western Europe. 71 1 



(fig-. 6) tapered evenly without any bulbous dilatation at the base, fringed on 

 their concave margins with exceedingly delicate cilia; margins of the laminae 

 produced between the ungues into small, sharp, triangular prominences; two 

 similar, but sharper and more slender prominences are situated on the extremity 

 beyond the last ungues. Length of the shell, '6 mm. 



Habitat— Ow an oyster-bed in Clif den Bay, Ireland, 4-6 fathoms; dredged off the 

 Eddystone lighthouse, and amongst the Scilly Islands, 10-40 fathoms (B. & R.); 

 off St. Monan's, Firth of Forth (Mr. T. Scott); Messina, inside the harbour, 

 8 fathoms (Dr. Dohrn) ; off Capri, Naples, 4 fathoms (A. M. N.). 



The very remarkable development of digltiform processes on the antennules is 

 the character which most decidedly separates this genus from its near ally, 

 Polycope, but the peculiar marginal denticulation of the shell, the trisetose 

 mandible-palp, and the very slight development of the post-abdominal inter- 

 unguial processes, are likewise of importance. We are indebted to the kindness 

 of our friend Mr. Thomas Scott for the opportunity of examining and figuring 

 freshly-taken specimens of this interesting species. We have thus been enabled 

 to amplify and amend the original description which -n as drawn up from a scanty 

 supply of dried specimens only. 



PLATYCOPA. 



Fam. CYTHERELLID-ffi. 



Shell oblong, obi on go-ovate, or ovate, highly calcareous, and very hard. Seen 

 from above, usually cuneate, or subcuneate ; greatest breadth posterior. No 

 rostrate process, or infero-anteal sinus. Valves unequal, the right the larger. 

 Antennules seven-jointed, first two joints longer than the following, geniculated 

 at their junction, following joints with numerous setae, but no specialized sensory 

 organ. Antennte (PI. lxvi., fig. 11) in form not unlike " the feet of Copepoda,''^ 

 flattened, consisting of two wide, sparingly setose basal joints, and two rami, one 

 two-, the other three-jointed, joints flattened and densely setiferous. " Mandibulae 

 minimae sed distinctae, palpo magno pectinatim setoso instructae. Membrorum 

 sequentium tria modo adsunt paria minime pediformia, anteriora duo branchialia, 

 posterius rudimentare " (Gr. 0. Sars), but in the male the second and third maxillae 

 are much more largely developed, and suited for prehension. Copulative organs 

 of the male elongated, cylindrical as in the Conchoeciadm. Posterior portion of the 

 body consisting of many segments (at least ten in the female), and furnished 

 dorsally with long setae. Caudal laminae small, fringed with setae, which are small 

 in front, but gradually increase in length backwards. Ova lodged within the shell 

 of the female 



5G2 



