1884.] DURING THE VOYAGE OF H. M.S. ' CHALLENGER. 337 



the lateral margin of the caudal shield on either side ; the median 

 portion of the three free abdominal segments projects freely as a 

 long spine. 



Station 161, 38 fathoms. 



9. Serolis minuta, n. sp. 



The * Challenger' collection contains only a single example of this 

 species ; it is a male, and measures 4 millim. in length by about 4 

 millim. in breadth, and is therefore the smallest known species. 



The dorsal portion of the fifth and sixth thoracic segments is 

 proportionately wider than in the other Australian species, the 

 diameter of the fifth segment being in fact hardly less than that of 

 the fourth. The suture which separates the sixth from the succeeding 

 segment is continued very nearly across the body; only a very small 

 portion remains fused with and inseparable from the succeeding first 

 abdominal segment. 



The epimera of the second and third abdominal segments are well 

 developed, and pass downwards along the caudal shield for about 

 one third of its length ; the first three epimera are closely approxi- 

 mated to each other, but the distal portions of the others project 

 freely ; the epimera of the two abdominal segments project further 

 downwards than the last pair of thoracic epimera ; the latter reach 

 about as far as the lateral notch on the caudal shield, where the 

 uropoda are attached. The first epimera show indications of division 

 into two parts. The posterior margin of the cephalic shield is 

 furnished with three blunt tubercles, of which the middle one is the 

 largest ; each of the succeeding segments is similarly produced into 

 a short tubercle at the median point of the posterior margin. 



The dorsal surface of all the thoracic segments except the first 

 is prolonged on either side into a flat triangular process, which 

 slightly overlaps the succeeding segment ; these processes, which are 

 hollow and serve for the attachment of the muscles moving the limbs, 

 are situated on the tergal portion of the segment close to its junction 

 with the epimeral portion. 



The caudal shield is almost triangular in shape and ends in a long 

 blunt spine ; the upper surface slopes gently down on either side 

 from the central keel. The terminal pair of appendages are attached 

 close to the upper end of the caudal shield. 



Station 161, 38 fathoms. 



Geographical Distribution. — The genus Serolis has a limited and 

 peculiar distribution ; it is almost entirely confined to the Antarctic 

 hemisphere. "With two exceptions — Serolis carinata, recently described 

 by Lockington as occurring on the shores of California, and Serolis 

 paradoxa, which is said to have been obtained on the coast of Senegal — 

 the shallow-water representatives of this genus are not found to range 

 further north than lat. 30° S. ; they inhabit the shores of all the con- 

 tinents and the principal groups of islands in this portion of the globe, 

 with the exception of the Cape of Good Hope, viz. Patagonia and the 

 Falkland Islands, the three Antarctic archipelagos (Marion Isles, the 



