564 Transactions. — Zooloijy. 



In the first place, all the specimens examined by me are 

 distinctively colom-ed, the males being of a uniform yellowish 

 colour, while the females are more or less of a deep-brown hue. 

 In some, nearly the whole upper surface is of a fine blackish - 

 brown colour ; in others, the pigment is broken up into scat- 

 tered but somewhat symmetrical patches on the cephalo- 

 thorax and various dorsal lamellae. All my female specimens 

 are about the same size, viz., 8mm., and the oviferous tubes 

 are about the same length. 



The vialc form of the species, according to Heller, is not 

 known, though he thinks "it is highly probable that Nogagu.s 

 latrcillii is the male, because similar spine-like projections 

 occur along the back in the median line, just as they do in 

 this female form." 



M. -Edwards's description of the species (" Hist. Nat. de 

 Crust.," vol. iii., p. 459) is not very satisfactory : — 



" Nogagus latreiUii. Frontal lamella greatly excavate; 

 carapace very large, and exhibiting on the posterior margin 

 on each side, very near the postero-lateral angle, a rounded 

 lobe which appears to belong to the first thoracic segment. 

 The first free articulation of the thorax is terminated laterally 

 by similar lobes, which are however very large and reach to 

 the middle of the penultimate thoracic segment ; this segment 

 bears similar small prolongations, which are almost com- 

 pletely hidden under the preceding lobes. Last segment of 

 thorax large, and armed on each side with two great conical 

 prolongations, which are directed conically backwards. Abdo- 

 men very short, 2-jointed, and terminated by rather large 

 natatory lamella)." 



Kroyer (" Bidr. t. Kundsk. om Snyitekrebsene," p. 242) 

 describes N. latreiUii and figures the female. Unfortunately, 

 his descriptions, being in Danish, are incomprehensible to me. 



I have drawn (Plate XXVII., fig. 1, c) a specimen of the 

 form taken along with the females of Pandarus armatus, and 

 which I assume must be the male of that species. The follow- 

 ing is a brief description : — 



Cephalothorax rather broader than long, less than half 

 the length of the body ; posterior margin nearly straight, 

 and toothed as in female but not so strongly, rather 

 rapidly contracted into somewhat acute arcuate postero- 

 lateral angles. Two succeeding segments short and only 

 slightly produced into lateral wings. Last segment of thorax 

 not more than half as broad as cephalothorax, rather longer 

 than broad. Abdomen about one-third as wide as preceding 

 segment, 2-jointed, last joint the longest, and produced on 

 the median line. Caudal laniellffi half as long again as abdo- 

 men, narrow, and each ending in 4 setae. 



Fourth pair of feet 2-branched ; inner branch 2-, outer 



