CRUSTACEA. 667 



Family XXVIII. Astacina. Four antennae inserted in nearly 

 the same transverse line, unequal, the middle with two setse, shorter. 

 Anterior feet chelate. Shell mostly hard, calcareous. Branchiae 

 fasciculate, composed of cylindrical filaments. 



Astacus G-RONOV., FABR. Lamellar appendage, dentiform or 

 hastate, mostly small, at the base of lateral antennae. Three first 

 pairs of feet didactylous, first pair large, thick. Caudal pinna with 

 lateral lamellae bipartite transversely. 



Nephrops LEACH. Scale at the base of external antennae longer 

 than the peduncle. Eyes large, reniform. Frontal rostrum elongate, 

 denticulate on both sides. 





Sp. Nephrops norwegicus LEACH, Cancer norwegicus L., DESM. Crust. PI. 37, 

 fig. i, GUERIN Iconogr., Crust. PI. 19, fig. i. 



Astacm LEACH (Astacus and Homarus lEcw.). 



a) Last segment of thorax mobile. Squama of external antennas 

 mobile, acuminate. Astacus. 



Astacus fluviatilis FABR., Cancer astacus L., RGESEL Ins. in. Suppl. 

 Tab. 54 6 i, GUERIN Iconogr., Crust. PI. 19, fig. 2, HERRICH-SCH.EFFER 

 Deutschl. Ins. Heft 186, Tab. 23 ; the cray-fish, river-cray ; attains a length 



^of 3" to 4". Of this species, which is dispersed almost over the whole of 

 Europe, there are some varieties which KOCH considers to be species. 

 HERRICH-SCH^EFFER 1. 1. Heft 140, 186. 



6) Last segment of thorax cohering with penultimate by an immove- 

 able connexion. Scale of external antennas small, dentiform. Gammarus 

 or Homarus. 



Sp. Astacus marinus, Cancer gammarus L., BASTER NatuurTc. Uitsp. n. 

 Tab. i. DESMAR. Crust. PI. 41, fig. i, the lobster, sea-cray ; on the coast of 

 Norway especially. 



Compare on the different species of this genus ERICHSON Archiv, 1846, 

 pp. 86103, 375377- 



Eryon DESMAR. (Fossil genus ; see DESMAR. Hist. nat. des Crust, 

 fossiles, p. 128.) 



Sp. Eryon Cuvierii DESM., BAJERI Oryctogr. nor. Tab. 8, Suppl. fig. i, 

 DESMAREST Crust, foss. PL 10, fig. 3, in the lithographic stone ; compare 

 BRONN Leth. geogn. pp. 473, 474. 



TJialassina LATR. Scale at the base of external antennae mostly 

 none, in a few very small. Four anterior feet, sometimes only 

 two, didactylous. Lateral lamellae of caudal pinna undivided. 

 Posterior part of abdomen or tail elongate. 



