214 TELEOSTEI. ACANTIIOPTEKTGII. 



parasitic on those animals. Van Beneden (Bull. Ac. Belg. 1870, 

 xxx, pp. 181-185) has shown that sometimes, at least, they prey 

 upon fishes, but they belong to the commensal division of parasite?, 

 and merely profit by the greater powers of locomotion possessed 

 by their host. 



The shape of the caudal fiu in these fifhes changes with age, as 

 in Elacate. 



Synopsis of Indian Species. 



Pairs of lamella; in disk 21-25 1. E. nauwates, p. 214. 



Pairs of lamellae in disk 17-18 2. E. rcmora, p. 215. 



Pairs of lamellae in disk 15-10 3. E. bracliypttra, p. 215. 



Pairs of lamellse in disk 12-13 4. E. albescent, p. 215. 



986. (1.) Echeneis naucrates. 



Echeneis naucrates, Linn. Syst. Nat. i, p. 44G ; Day, Fish. India, 



p. 257, pi. Ivii, fig. 1 (see synon.). 

 Nachuk, Marathi. 

 B. vii. D. 21-25*/83-41. P. 20. V. 1/5. A. 32-38. C. 17. 



Length of head 5 to 6, of disk 4| to 5, of pectoral 7| to 8, of 

 caudal fin 8, width between pectorals 10| to 11^, height of body 

 11| to 12| in the total length. Eyes transversely oval, 2| to 3 

 diameters in postorbital length of head, 2 to 3 from end of snout, 

 and 3| to 4| apart above. The disk is about as wide as long, and 

 contains from 21 to 25 transverse laminae, each having a tooth-like 

 posterior margin, whilst along the central line there runs a smooth 

 elevation, so that the vacuum may be confined to one half the disk. 

 The anterior laminae are directed slightly forwards ; those in the 

 second quarter of the disk are nearly transverse, and the posterior 

 slant backwards, the change in direction being very gradual. Out- 

 side the disk is a wide fleshy membrane, which extends behind to 

 over the occiput, but does not reach forward as far as the end of 

 the upper jaw. Maxilla extending to beneath the third lamina in a 

 specimen 2^ feet in length. Mandible pointed and covered above 

 with numerous rows of villiform teeth, forming a triangular toothed 

 space in front of the pointed upper jaw. Fins second dorsal and 

 anal opposite each other, both highest in front, where the rays are 

 | to | length of disk ; outer edge of both fins rather concave, and 

 the last rays slightly produced. Caudal with its posterior margin 

 straight, but having four short notches at its extremity. Lateral 

 line rather undulating. Colour generally brownish grey, exter- 

 nal margins of caudal and anterior tips of dorsal and anal fins 

 edged with white ; pectoral deep brown ; anal tipped with dark 

 brown ; centre of caudal nearly black. Sometimes a blackish band 

 along middle of side. 



Hob. Tropical and temperate seas generally ; attaining at least 

 et in length ; this is the commonest form in the Indian seas. 



* The first figures under D. in the fin formula of this genus represent the 

 number of pairs of kmell* in the disk. 



