536 



CRUSTACEA MALACOSTBACA. 



(= Astacus gammarus L.), the lobster. H. americanus M. Edw., 

 with 2 spines on under side of rostrum. Phoberus A. M. Edw. ; 

 Nephropsis W. -Mason, deep sea, with eyes reduced or ; Enoplome- 

 topus M. Edw. 



Thaumas- 

 flattened 



a 



FIG. 327. Young form (larva) of the lobster in mysis stage. 

 A', ^"antennae ; F' anterior ambulatory leg ; Kf" third 

 maxilliped ; R rostrum. (From Claus, after G. O. Sars.) 



Sub-fam. 2. 

 tochelinae. A 



rostrum : 1st trunk-legs 

 chelate and unequal, 2nd 

 chelate ; gills filamentous. 

 Thaumastocheles Wood- 

 Mason. 2nd antenna with 

 scaphocerite. T. zaleucus 

 W.-Suhm, has a right 1st 

 chela with enormously 

 elongated comb-like 

 divisions, and is blind. 

 Taken by the Challenger 

 from 450 fths. on Globigerina ooze. 



Sub-fam. 3. Potamobiinae. The fresh-water Crayfishes of the 

 N. Hemisphere. Carapace and uropods as above, but with the last 

 thoracic segment movable on its predecessor. The epipodial plate 

 of the first maxilliped without a branchia, but those of the 2nd-7th 

 thoracic feet with this plate plaited and bearing gill filaments on its 

 outer surface. Abdominal feet small, but all usually present, the 2 

 anterior pairs being modified in the male. Astacus M. Edw. (Potamobia 

 Leach). Britain to Japan, and N. America west of Rocky Mts. The 

 Crayfish of English streams, commonly called Astacus fluviatilis is, 

 according to Faxon, A. pallipss Lereboullet. Cambarus Erichson, 

 pleurobranchia absent from last thoracic segment. The crayfishes of 

 N. America, east of the Rocky Mts., including the blind C. pellucidus 

 (Tellkampf) of the Mammoth Cave of Kentucky. 



Sub-fam. 4. Parastacinae. The fresh-water Crayfishes of S. 

 Hemisphere. Epipodites of thoracic limbs not produced into a 

 lamina, except the first in which it bears gill filaments. Swimmerets 

 absent from the first abdominal segment, large in the succeeding 

 segments. AstacoidesGuerin, Madagascar ; Parastacus Huxley, Brazil ; 

 Paranephrops White, N. Zealand ; Astacopsis Huxley (including 

 Chaeraps Erichson) and Engaeus Erichson, Australia. 



Section 3. ANOMTJRA. 



A group near the border line between the Macrura and 

 Brachyura with great variety of form. In many the carapace 

 is broad. The trunk-legs of the last pair are weak and not used in 

 locomotion or for the prehension of food (Fig. 315, Tk. 8). The 

 sternum of the segment that bears them is free. The abdomen 

 is usually bent under the thorax, and except in the Thalassinidea 

 and Galatheidea, reduced. The 6th abdominal feet (uropods) 

 are often broad and natatory in these two tribes. In the others 

 they are reduced, and, in the Paguridea adapted for retaining 



