93 



arched over the eyes, and covering their peduncles", and he added: "Perhaps E. diomedece 

 might be better regarded as a variety of E. pellucida" . When I wrote the Monaco-paper quoted, 

 in which I mentioned " E. pellucida" and established three new species with tvvo pairs of lateral 

 denticles on the carapace, I had not seen any specimen agreeing with Ortmann's figure of his 

 E. diomedece. Later I received for study a splendid material collected by Prof. A. Agassiz in 

 the Pacific, and therein I found some specimens with a very large frontal plate and the rostrum 

 reduced. A subsequent examination gave the result that the specimens with this anomalous 

 frontal plate are mostly males and that their antennulae and copulatory organs agree completely 

 with the "Siboga" specimens possessing a normal, short, not expanded frontal plate terminating 

 in a well developed rostrum, and with specimens possessing a similar normal frontal plate and 

 rostrum from the Agassiz collection. Furthermore I found, that only a few specimens are typical 

 E. diomedece with the frontal plate so strongly expanded that it nearly covers the eye-stalks, 

 while other adult specimens from the Pacific have the frontal plate and rostrum intermediate in 

 shape between the typical E. diomedece Ortm. and the form shown in fig. 4 a. I conclude that the 

 expanded plate is a kind of variation, and the name E. diomedece is to be used for the species, 

 to which that variety belongs. All specimens in the "Siboga" collection are normal (fig. 4a). 



Distribution. — The species is widely distributed in the Indian Ocean and the 

 Pacific, but I have not seen any specimen from the Atlantic. 



7. Euphausia mutica H. J. H. PI. XIV, figs. \a — \d. 



1905. Euphausia mutica H. J. Hansen, Buil. Mus. Océan. Monaco, N° 42, p. 14 (partim). 



Stat. 12S. July 22. Lat. 4°2/'N., long. 125 257 E. 1645 m. Hensen vertical net, from 700 m. 



to surface. 10 specimens, subadult and adult. 

 Stat. 177'. September 1. Lat. 2°3o'S., long. I20, 28'E. Townet. 1 specimen. 



Description. — Frontal plate, rostrum and eyes nearly as in E. diomedece . The leaflet 

 from first antennular joint (fig. 1 a) shaped mainly as in E. diomedece, but presenting some minor 

 differences: it is scarcely or slightly more than half as broad as the end of the joint, directed 

 considerably forwards and upwards but only feebly outwards; the deep incision is less or not at 

 all oblique and the terminal spiniform processes are straight, not curved downwards in proportion 

 to the direction of the plate as is less or more the case in E. diomedece. The second antennular 

 joint on the upper surface without any vestige of protuberances near the distal angles. The anal 

 process is somewhat broad, in the male with three, in the female with four, spines decreasing 

 in size backwards. 



The copulatory organs show some minor and a couple of strong differences from those 

 of E. diomedece. The terminal process (figs. \b — \c) is long, a little more curved and less robust 

 as in E. diomedece, with the same spine somewhat before the end ; the proximal process is 

 shorter and more curved than in E. diomedece, its terminal fourth forming a rather large, oblong, 

 distally rounded plate (fig. 1 d), which on the inner side is proximally produced into an oblong 

 protuberance directed inwards and backwards (upwards) towards the origin of the process; 

 furthermore, when the whole organ is folded out (fig. 1 ö) this plate presents its surface and not, 



