902 CRUSTACEA. 



tarsi are much curved and have a seta below. The maxillipeds have 

 the penult joint broad. The eye is oval. 



Family GAMMARIDSE. 



The characters of the Gammaridse distinguishing them from the 

 Orchestidse have been pointed out, and here are only briefly reviewed. 

 Instead of the exceedingly short posterior stylets of the Orchestidse, 

 these stylets are elongated, and often extend backward beyond the 

 preceding pair; moreover, they are usually two-branched. Instead 

 of having no mandibular palpus, there is a long one- to three-jointed 

 palpus ; only in a rare instance is it wholly obsolete. Instead of 

 having the palpus of the inner maxillae small and one-jointed, it is 

 large and two- or three-jointed, and extends beyond the body of the 

 organ ; it is rarely simple. The few species of Gammaridse that have 

 no mandibular palpus, like the Orchestidae, are remote from that 

 family in the longer posterior stylets and in the palpus of the inner 

 maxillse. The maxillipeds terminate in a claw, as in Allorchestes, 

 the palpiform part being five-jointed. The epimerals may be as large 

 as in the Orchestidse; but there is a transition to the small size 

 found in the Corophidse. 



This family includes several subfamilies. 



In much the larger part of the genera, the base of the superior 

 antennse is slender. But there are a few in which it is thick and 

 short; and these species have large epimerals, a very compressed 

 body, a three-jointed mandibular palpus, a pointed, sparingly toothed 

 apex as the extremity of the mandible, quite unlike the denticulate 

 edge and accessory denticulate lobe of other Gammarids. Besides, the 

 inner lamellar process of the maxillipeds is large. The genus Lysi- 

 anassa is of this group, and we name the subfamily Lysianassinje. 



There is one Lysianassoid genus, with a short and stout base to the 

 inner antennse, large epimerals, and large inner lamella of the maxil- 

 lipeds, in which the mandibular palpus is one-jointed, with a denti- 



