406 ROBERT GURNET. 



the normal form, but bear only a single^ latei'al spine on 

 each side. The resemblance between the zoa^a of Corystes 

 and that of Thia polita as figured by Claus (76) and Cano 

 (91) is very striking, but the latter differs in having a much 

 longer lateral thoracic spine, and in having two lateral spines 

 on each fork of the telson. 



The colour and its distribution in the body are also charac- 

 teristic. The long dorsal spine is a rich orange colour, 

 deepest towards the tip. The rostrum has the same colour, 

 but the chromatopliores appear to be less numerous. The 

 labrum contains a dendritic black chromatophore, and similar 

 chromatopliores are found in the carapace, one above the 

 mandible, and two near the postero-ventral and postero- 

 dorsal edge of the carapace. A small orange chromatophore 

 lies at the base of the dorsal spine. The alimentary canal is 

 enveloped in black chromatopliores, which run back along it 

 as far as the end of the second abdominal segment. A large 

 ramified black chromatophore lies at the joint between the 

 third and fourth, fourth and fifth, and fifth and sixth abdo- 

 minal segments. To the naked eye the liver and gut appear 

 as a yellowish-black mass continued back as a black streak 

 through the thorax, and the orange colour of the spines is 

 conspicuous and distinctive. 



The appendages of the zotea are of the usual type, 

 differing in no important respects from those of Portunus, for 

 example, and do not need detailed description. 



The second maxilla (PI. 30, fig. 9) is the only cephalic 

 appendage Avhich calls for any remark. In it the exopodite 

 (scaphognathite) is characterised at this stage by the pos- 

 session of only five sette, the fifth springing almost directly 

 from the posterior edge, and not, as in Portunus, from the 

 end of a narrowed prolongation of the edge. 



' Since wiiling the above I liave found a single specimen in tlic second 

 stage of development, in which the left fork of the telson bears two lateral 

 spines as in Thia polita, wiiile the right fork bears but one. Tlie rarity and 

 nsymmetry of this structure seems to show that its presence is due merely to 

 an individual variation (see lig. 4j, 



