302 Prof. J. C. Schlodte on the 



apical face, -wliich, viewed from above, looks as if it had three 

 obtuse teeth ; the membranaceous portion is larger than on 

 the right mandible, but has only three digitiform lobes. 



24. Finally the elcutherognath type appears in a remark- 

 able modification in Lajyhystimj Kr., tlie only genus of sucking 

 Amphipoda -which I have hitherto been enabled to submit 

 to a close examination. It occurs behind the pectoral fins 

 of sturgeons, sharks, and the large cod ; and Kroyer de- 

 scribes it as " unicura, quod adliuc innotuit, inter Gammarina 

 animal parasiticum " (Naturh. Tidsskr. iv. p. 157). From his 

 point of view and by his method of investigation, we could 

 not expect that he should have understood that its mouth 

 really was constructed for suction ; at the same time his 

 excellent diagnosis lays proper stress both on the broad iigure 

 of the animal, and on its hooked claws well adapted for holding 

 on with, its " caput rostratum," the clumsy antennse with 

 their short stipites, the narrow mandibles, and the fact that 

 the palpus of the first pair of maxillte only consists of one 

 joint, that of the maxillipeds of two. 



The head is very small, with very prominent round eyes, 

 consisting of large, strongly convex, closely collected ocelli. 

 Viewed from the sides it presents but few features different 

 from those of the ordinary Gammarus-ty^Q ; nor do they at 

 once strike the observer. The elongate-triangular dorsal face 

 of the mandibles, the mandibular springs of the lower lip, the 

 position and arrangement of the two pairs of maxillas and the 

 maxillipeds, as well as of the clypeus and labram covering the 

 parts of the mouth in front, present at first sight nothing to 

 make us suspect any very remarkable peculiarities. On closer 

 examination, however, three points will attract attention as in- 

 dicating something out of the common, viz, : — first, the unusual 

 height of the forehead and the pleural margin of the head ; 

 secondly, the circumstance that the terminal two fifths of the 

 length of tlie mandibles are quite hidden by the upper lip ; 

 and, thirdly, that the lobes of the maxillipeds join the upper 

 lip with their apices and lateral margins so closely that the 

 lip and the lobes together form a beak-like eminence, which 

 stands out separately from its surroundings on account of the 

 great convexity of the lobes of the maxilli])eds and the small- 

 ness of their palpi, which are so much reduced in size that 

 they do not even reach quite to the lateral margins of the 

 upper lip. 



It is only when we examine the head from the front that 

 its peculiar rostrate configuration becomes clearly appreciable. 

 The outline of the face, strictly speaking, is a rhomb, en- 

 closed by almost straight lines ; the height from the apex of 



