CRUSTACEA FROM THE 'CHALLENGER' EXPEDITION. 39 



There are seven pairs of breeding -lamella at the base of the gnathopoda and pereiopoda, 

 increasing in size towards the end of the pereion. This also is quite the same thing as 

 has been seen in the Lophogastridse. 



The abdomen of Chalaraspis differs from that of the family just mentioned especially 

 by the absence of the pseudo-segment. The last segment of tbe pleon is elongated and 

 perfectly smooth. 



The pleopods are very perfect ; they have a strong basal joint and two rami. They 

 offer nothing particular either in the male or the female. 



The posterior borders of the quadrangular telson show a slight denticulation (fig. 1,6) ; 

 the outer appendages of the caudal fin are jointed. 



The males differ from the females only by being somewhat more slender and by the 

 absence of the breeding-lamellse. The small tubercle underneath the rostrum seems to 

 be more prominent in the males than in the females. 



Systematic Position of the Genus. 



Among the three families of Schizopods (Mysidse, Euphausiidse, and Lophogastridse) 

 hitherto known, this new form no doubt approaches most the latter, with which it 

 has in common the position and shape, of the branchiae, the breeding-lamellse, and the 

 pleopods ; but the presence of only four leg-like appendages, and the fact that four 

 pairs of appendages act here as maxillipedes, do not allow us to class it together with 

 them, as here both genera (Lophogaster and Gnathophausia) have got seven pairs of leg- 

 like appendages. It depends, of course, on what one considers the main point of view 

 from which a classification of the Schizopods ought to be made, whether from the form 

 and position of the branchise, or from the number of appendages which are transformed 

 to maxillipedes. I think the best plan is to carry on the hitherto accepted principle — to 

 establish different families for those groups in which there is a different number of leg- 

 like appendages. One should only deviate from this principle in case an animal should 

 be discovered which in every other respect is so closely allied to a certain group that the 

 conformation of the legs appears only as a very secondary acquisition ; but from what 

 we have hitherto seen of the steadiness in which the same number of maxillipedal 

 appendages is kept in forms which differ so much from each other as Gnathophausia 

 does from Lophogaster, or Petalophthalmus from Mysis, I doubt very much whether such 

 forms will ever be found. 



For the genus Glialaraspis one ought therefore to establish a separate family, Chala- 

 raspidse, holding its place between the Euphausiidee and Lophogastridse, and characterized 

 (until further discoveries show whether it has got several living members differing from 

 each other) by the 



Characters of the Genus. 



Chalaraspis*, n. g. 



Dorsal shield or carapace in no connexion with the posterior segments of the pereion ; 

 rostrum short, rounded ; eyes present ; no accessory eyes ; first antennae having a stout 



* XaXapos and aoiris. 



