SO Mr. P. W. Bassett-Smith on 



Mouth-organs are much the same as B. megaceros, B. tri- 

 ceros, &c, but between the basal joints of the first peraaopods 

 is seen an oval cavity with a ciliate margin. 



First perceopod with a strong basal joint bearing two 

 branches, the outer two-jointed, the inner three-jointed, 

 carrying plumose hairs. 



Second, third, and fourth perceopods two-branched, each 

 with three joints, the outer of irregular shape, from the outer 

 border of which spring short claws, on the upperside of these 

 one sees five to seven very strong teeth, and at the end a 

 short spur ; the terminal joints and inner borders have plumose 

 hairs as usual. 



Fifth perceopod single-branched, three-jointed, terminating 

 in three simple hairs, the middle being the longest; there is 

 also a fine hair placed halfway up this joint. 



Genital segment and can da! joints one third the total length, 

 slender and tapering, four in number, each joint wider than 

 long ; the terminal joint bears two elongated caudal plates, 

 giving off from the end one very long and one short bristle ; 

 also a minute hair on the outer side. 



Egg-sacs very large, as long as the whole animal; eggs 

 round, three in the diameter of sac. 



Length 3-4 millira. 



CaligidaB. 

 Hermilius, Hell. 



Hermilius longicornis, sp. n. (PL III. fig. 2.) 



This is the second known species of this genus, which was 

 formed by Dr. Heller in describing an animal with a peculiar 

 bivalve-shaped cephalothorax *. His specimens were found 

 on the gills of a " cat-fish " (Arius acuta), Java ; mine were 

 taken in quantity from the gills of another a cat-fish " (Arius 

 acutirostris) at Trincomalee. From almost all the fish 

 examined some specimens were obtained, the parasite being 

 very abundant ; it firmly clasps the gills with its folding-up 

 cephalothorax, being anchored by the strong hooks of the 

 second antennae; on examining the fish only the egg-sacs 

 are visible, their light colour causing them to be easily 

 detected. 



This species is readily separated from H. pyriventris, Hell., 

 by the great size of the posterior antennae and by the oblong 

 form of the genital segment. 



* ' Crustaceen : Reite der Fregatte Novara,' 1865. 



