CRUSTACEA FROM THE 'CHALLENGER' EXPEDITION. 35 



Salenia. Among the worms, which, unfortunately, usually come up in single and, in most 

 cases, spoiled specimens, we found some Annelids, a long Nemertean, and a very large 

 Balanoglossus* '. Crustacea there are many — Peneids, Caridids, a Pagurus, and the genera 

 Chalaraspis and JPetalophthalmus (which are described in this paper). Only one Brachi- 

 opod and several genera of Gastropods [JDentalium, Mitra, Pleuronectia, Neira, Limopsis, 

 and Cardium) belong to this fauna. There were also several fishes, one of which (the 

 Lophioid Ilelanocetus) certainly lives at the bottom in great depths. 



The Systematic Position 

 of our genus is easily fixed after what we have seen of its resemblances to Loplwgaster ; 

 for, after all that has been said about it, nobody, I am sure, will doubt that Gnathophausia 

 is a member of the family Lophogastridee. Now fortunately Sars has so well discussed 

 the affinities of Lophog aster, that the systematic position of our genus is easily under- 

 stood when we say that it is a Lophogaster with a free dorsal shield (like an Apus), with 

 a palpus on its first maxilla (like Nebalia), with accessory eyes on its second maxilla 

 and with subjoints in its pereiopods (like Ilysis). Gnathophausia, it is true, has many 

 peculiarities which are not found in the genus Lophogaster ; but I must nevertheless 

 maintain that it is closely allied to that form. The gnathopoda and pereiopoda all having 

 the shape of legs, the three branchiae, two of which are laterally covered by the carapace 

 and one not, and the presence of breeding-lamellae on all the legs, are fundamental cha- 

 racters which, according to our present systematical arrangement of the Schizopods, 

 assign it its place among the Lophogastridse. The subdivision of the sixth abdominal 

 segment, the shape of all the appendages and of the telson, are nearly exactly the same 

 in the two genera ; but there are other characters which Lophogaster has not, characters 

 which one might call atavistic ones ; and these are (1) the looseness of the dorsal shield, 

 (2) the presence of a palpus maxilla prima, (3) the subjoints in the legs, and (4) the 

 accessory eyes on the second maxilla. 



The subjoints in the pereiopods (3) have been hitherto only known as a peculiarity of 

 the genus Mysis, and the accessory eyes (4) as occurring in some genera of the Euphau- 

 siidse family. We therefore find characters united in Gnathophausia which were only 

 known separate in the two other families of Schizopods. Hereafter, however, Ave shall 

 find in a Mysid a character which until now was supposed to characterize only the 

 Lophogastridae, and shall see that these deep-sea forms of Schizopods combine in many 

 ways the characters of the shallow-water forms, the types of the hitherto acknowledged 

 families. But we shall also see that they can nevertheless be regarded as belonging to 

 those families (with the exception of one genus), as they have not a mere mixture of 

 characters, but are Mysids or Lophogastrids which possess some characters of the other 

 families. 



* Two fragments of this interesting -worm were got August 19, in lat. 5° 48' N., long. 14° 20' W., off the west 

 coast of Africa, from a depth of 2500 fathoms. The whole animal had prohably a length of 4 inches ; the head and 

 a piece of the body, however, were the only things we got. These fragments were very remarkable for the vivid 

 colours which they displayed : the head was yellow, the collar bright red, and the body of a yellowish red. Of this, 

 the Neapolitan species and the one which I discovered in the sand near Copenhagen, in shallow water, show nothing, 

 as they are uniformly white ; a priori one would have been inclined to suppose just the contrary. 



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