made during the Voyage of H. M.S. c Challenger. 3 575 



Stomatopoda are entirely confined to the shallower water of the tropical 

 and temperate regions. "We never met with one far away from the land, 

 though their young stages are widely spread all oyer the surface of warmer 

 seas. 



The most interesting Crustacea wh'ich have been got are undoubtedly 

 the Schizopods, several new genera of which were brought up, which are 

 both interesting for anatomical and physiological reasons. These have 

 been partly figured in 'Nature' (Gnathophausia, 'Nature,' 1873), and 

 afterwards fully described by me in a paper " On some Atlantic Crus- 

 tacea," which has been or will be published by the Linnean Society. Here 

 only a few words about them. 



The normal Schizopods, as is well known, have their carapax fixed to 

 the pereion, with the exception of the aberrant genus Nebalia, in which 

 the latter is unattached, and resembles a shell enclosing the anterior por- 

 tion of the body. Our deep-sea genera, however, have (at least most of 

 them) a carapax which is neither the one nor the other, but resembles 

 very much the shield-like carapax of the Phyllopod genus Apus. In 

 other respects they are, however, nearly allied to the established families, 

 though some of them have characters which are peculiar to several of the 

 shallow-water forms, but have as yet not been found united in one genus. 

 Moreover some of these abyssal Crustacea are blind, or show peculiar 

 modifications of the organs of sight, as well as of the chitinous outer parts, 

 which have lost the optical apparatus. 



Petalophthalmus inermis is the name which I have given to the most 

 remarkable of these Schizopods, as in it the optical apparatus of the eye 

 is entirely wanting, while its chitinous parts have remained in the shape 

 of a concave plate-like organ supported by a peduncle. This plate shows 

 neither a trace of the organs of vision nor any appendages ; it consists of 

 a double chitinous layer, and nothing is to be seen in it but the fluid of 

 the body and the attachment of the muscles, which are to be found in all 

 stalked-eyed Crustacea. Its appendages show this form to belong to the 

 family Mysidse, there being six legs (second gnathopod and the five pereio- 

 pods), no branchiae, large breeding-lamellae in the female, and only rudi- 

 mentary pleopods in the male. The carapax, as we have said above, leaves 

 in both sexes five segments entirely uncovered. 



But besides the looseness of the carapax there are peculiarities in the 

 male of this Schizopod which have been found nowhere else ; for its first 

 antennae, the palpus mandibularis, the maxilliped, and the first gnathopod 

 have been converted into enormous prehensile organs, and the latter shows 

 a large lamellar appendage like the maxilliped in the female. These 

 elongated appendages have in the male six times the length which they 

 have in the female. 



This is the only'Mysid which was got from great depths (1900 and 

 2500 fathorns), .The next family, the Euphausiidae, was represented by a 

 very large species, red and opaque, which came up in the South Atlantic 



vol. xxiv. 2 T 



