CRUSTACEA. 667 
Family XXVIII. Astacina. Four antenne inserted in nearly 
the same transverse line, unequal, the middle with two sete, shorter. 
Anterior feet chelate. Shell mostly hard, calcareous. Branchize 
fasciculate, composed of cylindrical filaments. 
Astacus Gronov., Fasr. Lamellar appendage, dentiform or 
hastate, mostly small, at the base of lateral antenne. ‘Three first 
pairs of feet didactylous, first pair large, thick. Caudal pinna with 
lateral lamelle bipartite transversely. 
Nephrops Leacu. Scale at the base of external antenne longer 
than the peduncle. Eyes large, reniform. Frontal rostrum elongate, 
denticulate on both sides. 
Sp. Wephrops norwegicus Luacu, Cancer norwegicus L., Dusm. Crust. Pl. 37, 
fig. 1, GuéRIN Iconogr., Crust. Pl. 19, fig. r. 
Astacus Lracn (Astacus and Homarus Epw.). 
a) Last segment of thorax mobile. Squama of external antennz 
mobile, acuminate. Astacus. 
Astacus fluviatilis Fasr., Cancer astacus L., Raset Jns. 11. Suppl. 
Tab. 54—61, GuERIN Iconogr., Crust. Pl. 19, fig. 2, HmRrRicH-ScH@®FFER 
Deutschl. Ins. Heft 186, Tab. 23; the eray-fish, river-cray ; attains a length 
of 3” te 4”. Of this species, which is dispersed almost over the whole of 
Europe, there are some varieties which KocH considers to be species. 
HERRICH-SCHHFFER I. 1. Heft 140, 186. 
6) Last segment of thorax cohering with penultimate by an immove- 
able connexion. Scale of external antenne small, dentiform. Gammarus 
or Homarus. 
Sp. Astacus marinus, Cancer gammarus L., BasteR Natwurk. Vitsp. 11. 
Tab. 1. Desmar. Crust. Pl. 41, fig. 1, the lobster, sea-cray ; on the coast of 
Norway especially. 
Compare on the different species of this genus ERICHSON Archiv, 1846, 
pp: 86—103, 375—377- 
Eryon DEsMaR. (Fossil genus; see Desmar. Hist. nat. des Crust. 
fossiles, p. 128.) 
Sp. Eryon Cuviertti DEsM., BAJERI Oryctogr. nor. Tab. 8, Suppl. fig. 1, 
DeEsMaREsT Crust. foss. Pl. 10, fig. 3, in the lithographic stone ; compare 
Bronn Leth. geogn. pp. 473, 474- 
Thalassina LAtR. Scale at the base of external antenne mostly 
none, in a few very small. [our anterior feet, sometimes only 
two, didactylous. Lateral lamelle of caudal pinna undivided. 
Posterior part of abdomen or tail elongate. 
