481 



specimens at Haugesund. It is by do means very active in its movements, 

 and, when swimming abont, carries the 2 anterior pairs of pereiopoda spread 

 out in a peculiar manner to each side. 



Bistrihidion. — Shetland Isles (Norman), British Isles (Robertson), 

 coast of France (Chevrenx), Adriatic (Grube), Mediterranean at Messina (the 

 author), Azores (Barrois). 



Fam. 20. Gammaridae. 



Body more or less slender, with the segments of urosome well defined. 

 Coxal plates of moderate size, or very small. Antennae generally rather 

 slender, and, as a rnle, but little different in the two sexes, the superior 

 ones pi'ovided with an accessor^' appendage often greatly developed. Oral 

 parts normal, except in the genus LilJjchorgia. Gnathopoda generally rather 

 powerful and subcheliform, being, as a rule, much more strongly built in 

 male than in female. Pereiopoda more or less slender, the 3 posterior pairs 

 generally increasing in length, and having the basal joint laminar. Last 

 pair of uropoda, as a rule, projecting beyond the others, and having 

 the rami more or less foliaceous. Telson generally small, lamellar, and 

 more or less deeply cleft. 



Memarks. — The present family comprises a great number of Amphi- 

 poda, which on the whole ma}' be said to exhibit most prominently the 

 typical features of the order. Yet there are some forms, which differ more or 

 less from the type, as revealed in the genus Gaminarus, and which exhibit, 

 as it were, transitions to other families. Thus the genus MelphiiJippa would 

 seem to approach the Atylidcp, whereas the genus Lilljeborgia shows some 

 resemblance, especially in the structure of the oral parts, to the Leucothoidcc , 

 with which family it was in fact associated by Boeck. Perhaps the 2 above 

 named aberrant genera should more properly be wholly removed from the 

 present family, and be regarded as types of 2 separate families. In such case 

 indeed, the family Gammaridce should have been much more precisely defined. 

 I feel, however, some hesitation in increasing the number of families, especially 

 where such families would be founded only upon isolated genera, and I 

 therefore prefer provisionally to include the said genera in the family Gam- 

 maridos, placing the one at the liead, the other at the end. The family com- 

 prises 12 Norwegian genera, two of which are now for the first time 

 established. 



fi" — Crustacea. 



