of the North Atlantic and of North-Western Europe. 673 



Fam. II.— RUTIDERMATID-ffi. 



Shell oval, truncate behind, antennal sinus very shallow, no overhanging 

 rostral process, surface of valves rugose. Antennules without sensory organ. 

 Antennae without any secondary branch. Mandibular palp, with last joints of 

 great size, forming a large chela. No branchise. 



Genus RuTiDERMA,* n. g. 



Shell oval, truncate behind, antennal sinus very small, no overhanging rostral 

 process ; surface of valves in type species rugose. Antennules (PI. lviii., fig. 12) 

 without sensory appendage, a ringed seta taking its place. Antennse (fig. 13) 

 without any secondary bi'anch. Palp of mandible (fig. 14), with last joint very 

 massive, terminating in a strongly developed chela, formed by two very large 

 processes, which are hooked at their extremities, the outer one flattened and 

 pectinated on its inner face. Outer tooth of second maxillae three-lobed, lobes 

 plain-edged. Caudal laminae (fig. 16) having few ungues. 



The shell approaches in form to that of Sarsietla, but is oval instead of round, 

 and the infero-posteal corner only slightly prominent ; while anteriorly there is an 

 antennal sinus of small size. The structure of the palp of the mandible is most 

 remarkable. The account we give of the animal is derived from the maceration of 

 specimens which have been preserved in a dried state for twelve years, many 

 minute details, therefore, are wanting, and some of those given perhaps will prove 

 to be not absolutely correct. 



Rutiderma compressa, n. sp. 



(Plate LVIII., figs. 9-16.) 



General form of shell of ? oval, vertically truncated behind. Ventral 

 margin well arched throughout to the infero-posteal angle; dorsal margin also 

 boldly and evenly arched, but with very slight sinuses in two or three 

 places, more especially just before reaching the supero-posteal corner ; hinder 

 extremity broadly truncated and bilobate, so as to leave a slight central 

 sinus ; anterior extremity rounded ; antennal sinus very small and shallow, its 

 upper margin forming a right angle with the bottom of the sinus, there being 

 no vestige of a beak. Surface of valves very irregular, punctated with foveolae 



* pvTis, a wrinklu ; Sepfna, the skin. 



