190 Mr. S. I. Smith on the Abyssal 



The first question which arises in discussing the bathyme- 

 trical habitats of the species in this list is: Which of them 

 actually inhabited the bottom, or the region near the bottom, at 

 the depths from which they are recorded, and what depths do 

 the remaining species inhabit ? That none of them are truly 

 pelagic surface species may, I think, be taken for granted, for 

 with the single exception of Acanthepliyra Agassizii none of 

 the free-swimming species have been taken anywhere near 

 the surface. 



The first fifteen species in the list, and 45 and 46 as well, 

 are unquestionably inhabitants of the bottom, and never swnm 

 any great distance from it. Nos. 16, 17, 18, and 47, though 

 species which may swim freely for considerable distances from 

 the bottom, undoubtedly rest upon it a part of the time, the 

 structure of the perasopods being fitted apparently to do this. 



The species oi Acanthepliyra j Oplophorus^ Evhyrina^ Noto- 

 stomuSf Meningodora, and Hymenodora.^ wdiich are very much 

 alike in the structure of the articular appendages and branchias 

 and are here grouped together as Miersiidte, are among the 

 most common and characteristic forms taken in trawling at 

 great depths ; and it is perhaps doubtful whether any of them 

 are, strictly speaking, inhabitants of the bottom. The occur- 

 rence at the surface of a living and active specimen of Acan- 

 thephyra Agassizii shows that this species at least is capable 

 of living at the surface in water of a temperature more than 

 thirty degrees higher than that of the abyssal depths. Such 

 facts make it very difiicult to draw any conclusions from the 

 mere finding of specimens of any free-swimining species in 

 the trawl coming from particular depths, and we are compelled 

 to resort to the structure of the animal itself for evidence as to 

 the depth of its habitat. The highly-developed black eyes, 

 the comparatively small eggs, and the firm integument of 

 Acanthephyra Agassizii and A. eximia are some evidence, 

 though perhaps inconclusive, that these species do not nor- 

 mally inhabit the greatest depths from wdiich the former 

 species has been recorded ; and neither the length nor the 

 structure of the perteopods shows special adaptation for resting 

 on soft oozy bottoms. We are therefore led to conclude 

 that these two species normally inhabit the upper part of the 

 vast space between the surface and bottom regions. The 

 similarity in the structure of the perasopods in all the species 

 of the genus except A. gracilis apparently indicates similarity 

 in habits ; but the imperfectly developed eyes and soft integu- 

 ment of A, microphthahna and A. hrevirostris are evidence 

 that these species inhabit greater depths than A. Agassizii 

 and A. eximia^ and that they are trttly abyssal if not bottom- 



