RECENT BRITISH OSTRACODA. 



4.33 



long simple setse ; lower antennae four-jointed, the third joint long and narrow ; flagel- 

 lum long and biarticulate. Mandibular palp three-jointed, bearing a distinct branchial 

 appendage. Lowest seta of the branchial plate of the first pair of jaws deflexed. Peet 

 long and slender, alike in male and female. Abdomen terminated by a hairy conical 

 process ; postabdominal lobes bearing two moderately long subequal setae. 



The genus is well characterized by the oblique "peach-stone " outline of the carapace, 

 and by the very slender, setose but non-spinous limbs of the animal. The typical form 

 is well represented by the species described by Dr. Baird under the name Cythere im- 

 pressa, w^hich is common both in a recent state and in the posttertiary formations of 

 England, Scotland, and Norway. 



1. LoxocoNCHA iMPRESSA (Baird). (Plate XXV. figs. 35-40, and Plate XL. .fig. 4.) 

 Cythere impressa, Baird, Brit. Entom. p. 173, t. xxi. fig. 9. 



viridis, Lilljeborg, De Crustaceis, p. 168, tab. xviii. figs. 4-6 & 8-13, and tab. xix. figs. 3-5. 



flavida, Zenker, Ueber die Krebstbiere, p. 86, tab. v.b. 



carinata, Brady, Ann. & Mag. Nat. Hist. vol. xvi. (1865) p. 190, pi. ix. figs. 1-4. 



rhomhoidea, Fiscber, Abbandl. d. bayerischen Acad. d. Wissenscbaften, Bd. vii. p. 656 {fide G. O. 



Sars). 



Loxoconcha rhomhoidea, G. O. Sars, loc. cit. p. 62. 



British, type. Distribution: Recent — Norway, Great Britain, Ireland, Bay of Biscay. Fossil- — Glacial 

 deposits and raised beacbcs, Norway, Scotland, England, and Ireland. 



Carapace oiih.e female, as seen from the side, rhomboidal ; greatest height in the middle, 

 equal to two-thirds of the length ; extremities obliquely rounded, the posterior obliquely 

 truncate above the middle; superior strongly arched, inferior sinuated in front of the 

 middle, and prominently keeled behind*. Outline, as seen from above, tumid, widest in 

 the middle, and tapering evenly to the extremities, which are sharply pointed ; width 

 equal to somewhat more than half the length. The shell of the male is much lower in 

 front than behind, the dorsal margin straight, and angular at the anterior and posterior 

 extremities ; outline as seen from above considerably less tumid than in the female. 

 Surface often covered with a thick calcareous crust, and marked with closely set im- 

 pressed puncta, which are arranged in more or less regular concentric rows. Young- 

 specimens bear in the intervals of the pittings distant elevated papilla). Hinge-processes 

 very feebly developed, intervening margin crenulated. Colour yellowish white, and, 

 when occurring in tidal pools or amongst seaweed, marked with rather large brown spots. 

 Upper antennte very slender ; the second joint pilose on its anterior margin, and shorter 

 than the united lengths of the two following joints ; last two joints about equal in length, 

 each bearing at its apex three or four very long slender setae. Third joint of the 

 lower antennae long and narrow, bearing two setae above the middle of the posterior 

 margin, and finely serrated below. Second joint of the last pair of feet about equal to 

 the conjoined length of the two following joints ; last joint finely toothed on its anterior 



* In my paper ("Fossil Eiitomostraca from the Brick-earth of the Nar") the anterior extremity of C. carinata 

 is erroneously de.scribed as the posterior, and vice versd. 



VOL. XXVI. 3 N 



