CRUSTACEA FROM THE 'CHALLENGER' EXPEDITION. 29 



segments of the pereion. On its upper surface there are five longitudinal ridges and two 

 transverse sulci, which can best be understood from the figures (PI. X. figs. 2 & 2 a), 

 These ridges divide the carapace into five regions, which we might call the regiones 

 cephalica, hepatica, cardiaca, branchialis, and marginalis. I think it unnecessary to <>ive 

 for each the exact dimensions. 



In front there is a cleft for the pedunculated eyes, above which there is a sharp spine ; 

 laterally, above the cleft, which is occupied especially by the second maxilla, there is 

 another spine. The lateral edges are more or less flattened, and form two " rounded 

 plates," as Sars calls them in his paper on Lophogaster*, between which there is the 

 just-mentioned cleft. This can best be explained by PL X. fig. 3, where I have figured 

 the parts of the mouth and the upper lateral edges of the dorsal shield, seen from below. 

 There the upper plate {x), to which are attached the muscles of the oral apparatus, covers 

 to some extent the mandible ; the lower plate (y) protects the palpus and the accessory 

 eye of the second maxilla from behind. 



In Lophogaster there is also to be seen a rudiment of a rostrum and the longitudinal 

 ridge (Sars, fig. 1). The lateral spines are very much like those of Gnathophausia ; the 

 lateral edges of the shield, however, are not prolonged to such an extent backwards as in 

 our genus, and the posterior margin leaves, as has been mentioned already, two segments 

 entirely free. 



The eyes issue from between the rostral portion of the shield and the base of the inner 

 antennae ; they have a length of 8 millims., and show two joints in their peduncle. 



The inner antennae consist of a short and stout funiculus and two flagella. The funi- 

 culus is four-jointed, and attains a third of the length of the squamiform appendage of 

 the outer antenna. It is twice the diameter of the eyes in width, and is densely covered 

 with hairs on its inner side. The exterior flagellum is very long (130 millims.), and flat- 

 tened at its base (2 millims.), but the interior flagellum rounded and mucli shorter (length 

 40 millims.). Underneath and behind the inner antennas is the large base of the squami- 

 form appendage, showing outside a strong spine. The appendage itself entirely covers the 

 funiculus, and has a length of 19 millims. : its inner border is even, but densely covered 

 with hairs ; the outer one has at the base a rounded prominence, and further on four 

 sharp spines, in addition to the top spine. A longitudinal ridge (a trace of which may 

 also be seen in the cordiform appendage of Lophogaster — Sars, fig. 13 e) divides the 

 appendage into a larger and a smaller portion. Underneath this appendage we see a 

 three-jointed long funiculus of the exterior antenna (length 5 millims.), the flagellum of 

 which has the length of the shorter one of the inner antenna (40 millims.). 



Oral apparatus. (Plate X. fig. 3.) 

 The upper lip is a large cordiform plate (6|- millims. in length by 5 millims. in width), 

 the top of which reaches upwards to the first joint of the antenna? interioris funiculus. 

 A short groove descends from its centre towards the mouth ; this organ is nearly of the 

 same shape here as in Lophogaster (Sars, fig. 17). Very Lophogaster-]ike are also the 

 strong mandibles (fig. 3, md), to which are attached two three-jointed palpi, the inner 



* ' Beskrivelse over Lophogaster typicus ' (Christiania, 1862), pi. i. figs. 3 & 4, and p. 2. 



