PRESENT AND PAST RELATIONS 257 



such as crabs of the typical northern genera Homola, 

 Latreillia, and Maia, and characteristic northern 

 shrimps like Crangon, Pandalus, and PasiphcEa. 



So far as they have been named, the Investigator 

 deep-sea species belong to the following groups : — 



Species. 



1. Cirripedia (barnacles) . 2 



2. Amphipoda (sand-hoppers) 4 



3. Isopoda (sow-bugs) . . 2 



4. Stofnapoda (locust-shrimps) 3 



5. Schizopoda (pouch-bearing 



shrimps) . . .9 



6. Peneidea (prawns) . . 27 



7. Caridea (shrimps) . .58 



8. 5'/(?«o/z</(?<3' (sponge-prawns) 3 



Species. 



9. Astacidea (lobsters) . 20 



10. Thalassinidea (scorpion- 



lobsters) . . .10 



11. Paguridea (hermit-crabs) 13 



12. Galatheidea (hermit- or 



coral- lobsters) . . 39 



13. Dromides (sponge-crabs) 9 



14. Oxystome crabs . .16 



15. True crabs . . .28 



Just as with the fishes, the higher Crustacea of 

 the deep sea, though they do not include, as it was 

 at one time expected that they would, any abiding 

 relics of long-past geological ages, yet as a whole 

 form a slightly more antiquated assemblage than 

 those of the shore. This is specially noticeable in 

 the case of the highest order Decapoda, in which 

 group we still find survivors of the elsewhere-extinct 

 Triassic family Eryonidce, and a remarkable exuber- 

 ance of such archaic and primitive stocks as the 

 Peneidea and Caridea, along with a suggestive paucity 

 of the highest and most recently evolved tribes of crabs. 



In the following paragraphs we shall consider some 

 of the ways in which the Crustacea of the nether 



