ENTOMOSTRACA. [ 289 ] 



ENTOMOSTRACA. 



tennse two pairs, large : eyes stalked 

 (PL 19. fig. 28). 



Fam. 3. DITHYBIDA. Bivalve. 

 Limnadia, Estheria, Limnetis. 



Order 2. Cladocera. Legs four to six pairs, 

 chiefly branchial; eye single, and very 

 large ; antennae two pairs, inferior large, 

 branched and adapted for swimming. 



Fam. 1. DAPHNIAD^J. Superior antennae 

 small; inferior large, two-branched; 

 legs five or six pairs, all enclosed within 

 the carapace ; eye single, large. 



* (Daphnina.) Legs five pairs ; inferior 

 antennae two-branched, one branch four-, the 

 other three-jointed. 



Daphnia. Head produced below into 

 a beak ; superior antennae very small 

 (PL 20. fig. 28). 



Moina. Head rounded and obtuse ; su- 

 perior antennas large (PL 19. fig. 26). 



Macrothrix. Head beaked, beak di- 

 rected forwards ; superior antennae 

 one-jointed, hanging from the beak 

 (PL 19. fig. 25). 



Bosmina. Head terminating in a sharp 

 direct beak ; superior antennae long, 

 many- jointed, projecting from end of 

 beak (PI. 20. fig. 2). 



Drepanothrix, Lathonura, Acantholeberis, 

 Ilyocryptus. 



** (Sidina.) Legs six pairs ; inferior an- 

 tennae two-branched ; a row of spines arising 

 from the edge of larger branch; superior 

 antennae of moderate size. 



Sida. One branch of inferior antennae 

 three-, the other two-jointed (PL 19. 

 fig. 27). 



Daphnella. Both branches two-jointed 

 (PL 20. fig. 27). 



Fam. 2. POLYPHEMIDJE. Inferior antennae 

 two-branched, one branch four-, the 

 other three-jointed; lower part of shell 

 forming a large vacant space for con- 

 taming the ova and young; eye very 

 large; legs four pairs, not contained 

 within the shell. 



Polyphemus. Tail-like abdomen project- 

 ing outside the shell : freshwater (PL 

 19: fig. 29). 



Evadne. Abdomen scarcely projecting 

 from the shell ; marine (PL 19. fig. 30). 



Fam. 3. LYNCEID^. Superior antennae 

 very short ; inferior of moderate size, 

 branched, each branch three-jointed; 

 legs five pairs ; eye single, with a black 

 spot in front ; intestine convoluted, 

 having one complete turn and a half. 

 Eurycercus. Shell subquadrangular, ab- 

 domen forming a flat, densely serrated 

 plate (PL 20. fig. 39). 

 Chydorus. Nearly spherical; beak very 

 long, sharp, and curved ; inferior an- 

 tennae very short (PL 20. fig. 7). 

 Camptocercus. Ovoid ; abdomen long, 

 slender, and very flexible, serrated (PL 

 20. fig. 4). 



Acroperus. Somewhat harp-shaped, with 

 an anterior inferior obtuse angle ; infe- 

 rior antennae rather long (PL 19. figs* 

 1,2). 



Alona. Quadrangular, striated or grooved 

 longitudinally; inferior antennae short 

 (PL 19. figs. 4, 5). 



Pleuroxus. Gibbous above and anterior- 

 ly ; obliquely truncate below ; first pair 

 of legs very large (PL 19. fig. 32). 

 Peracantha. Oval, lower end with a 

 curved posterior point, fringed infe- 

 riorly and antero-superiorly with strong 

 hooked spines (PL 19. fig. 31). 

 Monospilus. 



See CRUSTACEA and SIPHONOSTOMA. 

 BIBL. Baird, Br. Entom. ; M. -Edwards, 

 Crustac. iii. ; Straus, Mem. Mm. 1819, v. 

 380, and 1821, vii. 33; Koch, Deutschl. 

 Crustac. ; Desmarest, Crustac. ; Jones, En- 

 tom. Cretac. Form. (Palceont. Soc.); Entom. 

 Tert., and Foss. Esthetics ; Zencker, Mullens 

 Archw, 1851 (Micr. Tr. i. 273) ; Morris, 

 Brit. Foss. 98 ; Lubbock, Linn. Tr. xxiii. 

 176, and xxiv. 197 ; Dana, Classif. Crust. 

 1853, Report on Crust. U. S. Exped. 1855 ; 

 Baird, Ann. N. Hist. 1862, ix. 132, and*. 1; 

 Grube, Esth. u. Limnad., Archiv Nat. xxxi. 

 1865 ; Plateau, Ann. N. H. 1869, iii. 12 ; 

 Schoedler, Cladocera (3 pi.), 1863; Brady, 

 Ann. N. H. 1864, xiii. 59 (New Ostracoda) ; 

 1868, ii. (Ostr. from Scandinavian Seas, 

 Mauritius, #c.); 1869, iii. 45; id. Linn. Tr. 

 1868, xxvi. 353 (Monogr. Ostracoda) ; and 

 Copepoda (Ray Soc.) ; Norman and Brady, 

 Monogr. 1867; Sars, Oversigt af Norges 

 Mar. Ostrac. 1865 ; Lilljeborg, De Crusta- 

 ceis, 1853; Zencker, Mull. Arch. 1850 (Cty- 

 pris) ; ibid. 1851 ; id. Arch. Naturg. 1854 ; 

 Hartog, Jn. Mic. S. 1880, 243 ; Brady and 

 Robertson, Ann. N. H. 1872, ix. 48 ; & Tr. 

 Palaontog. Soc. xxviii. ; Glaus, Copepoda t 

 1881 j and the BIBL. of the genera. 



