384 



the posterior ones much stronger and imperfectly subcheliform. Pereiopoda 

 very strong and subequal in length, propodal joint in all rather large and 

 swollen, dactylns extremely powerful, hook-shaped. Branchial lamellae small. 

 Uropoda nearly naked, last pair but slightly differing from the preceding 

 pairs. Telson rather small, rounded at the tip. 



Remarks. - - This genus was established by Kroyer as early as in the 

 year 1842, to include a peculiar Amphipod found by him, parasitic, on the 

 skin of the common sturgeon. The genus Dartvmia of Sp. Bate is undoubt- 

 edly identical with the Kroyerian genus, and this evidently is also the case 

 with the genus IchfliyomyzocMS of Hesse. The latter author describes and 

 figures no less than 4 different species, one of which may be that upon which 

 Kroyer founded his genus. There would thus seem to exist at least 4 

 different species belonging to this genus. All the species live as true parasites 

 on the skin of several kinds of fish, to which they cling firmly by the 

 aid of the strong hook-like dactyli of the pereiopoda. To the fauna of Nor- 

 way belongs, as yet, only a single species, to be described in the sequel. 



1. Laphystius sturionis, Kroyer. 



(PI. 134). 



Laphystius sturionis, Kroyer, Nat. Ticlsskr. 1 R. Bd. IV, p. 157. 

 Syu. : Darwinia cornpressa, Sp. Bate. 

 Ichthyornyzocus morrhuae, Hesse. 



Body rather stout, with the back quite smooth and broadly vaulted. 

 Cephalon comparatively small, depressed, rostral expansion narrowly truncated 

 at the tip, and reaching about to the end of the basal joint of the superior 

 antennse. The 3 anterior pairs of coxal plates successively increasing in size, all 

 rounded quadrangular in form, and about as deep as the corresponding segments; 

 4th pair very unlike the preceding pairs, nearly twice as deep, and having the 

 outer part acutely triangular; the 2 succeeding pairs having the posterior lobe 

 produced to an accuminate deflexed projection. Last pair of epimeral plates 

 comparatively rather small and narrow, with the lateral corners obtuse-angled; 

 those of the 2 preceding pairs produced to a short recurved point. Urosome much 

 flattened and considerably instricted at the base. Eyes of moderate size, rounded, 

 and placed each within a lateral nodiform prominence of the cephalon, pig- 

 ment very dark. Superior antennse scarcely exceeding in length Y* of the 

 the body, joints of the peduncle rather tumefied and nearly equal in size, 

 flagellum about the length of the peduncle, and composed of only 9 articulations 

 successively diminishing in breadth, and each having, anteriorly, a dense fascicle 

 of delicate sensory bristles. Inferior antennse much smaller than the superior 



