L '21. 40 



between two extremes ; (a) those in which there is a very high 

 and prominent median crest, separated from an outer and 

 inner lateral keel by deeply hollowed spaces- which are practi- 

 cally smooth except for a few granules near the proximal end 

 and (b) those in wiiich the median crest and lateral keels are 

 so reduced as to be almost indiscernible and the surface of the 

 hand is almost flat and covered throughout wdth granules. In 

 those specimens in which the median crest and lateral keels are 

 present the dorsal surface of the dactyl is slightly hollowed out. 

 The keel on the inner edge is higher than that on the outer, 

 and all three keels are usually more or less serrate. The palm 

 is slightly longer than the fingers. 



In the left cheliped the merus is laterally compressed, wath 

 a rounded upper edge. The carpus is also compressed but 

 its upper edge bears a row of ten or tw^elve strong teeth in- 

 creasing slightly in size distally ; there are also a few smaller 

 teeth at the side of this row\ The propodite has a line of 

 strong teeth along the outer margin, and also a slight median 

 keel furnished with prominent teeth. Between the median 

 keel and the outer edge the surface is tuberculate ; between the 

 keel and the inner edge, however, it is smooth. The fingers 

 are longer than the palm and end in yellow claws. The 

 median keel is highest in the proximal part of the joint and 

 and becomes less distinct distally but can still be traced almost 

 to the tip of the fixed finger. The dactyl is smooth except for 

 a few small denticules on the outer edge. The form of the 

 left cheliped remains constant and does not vary wdth the right. 



The w^alking legs, as usual, are strongly compressed laterally* 

 On the right leg of the first pair there is a row^ of about ten 

 strong teeth on the upper edge of the carpus, and from twelve 

 to fourteen on the propodite. The dactyl is longer than the 

 propodite, curved and tapering ; there are no spines on the 

 lower> edge ; it is fringed with setae, above and below. On 

 the left leg of the first pair, the teeth on the carpus and propodite 

 are less numerous, being reduced to about eight on either joint. 



The walking legs of the second pair are very similar to those 

 of the first, the only difference being that the teeth on the 

 carpus and the propodite are much feebler, especially in the 

 case of the left leg. 



The fourth and fifth pereiopods exhibit no characters pecu- 

 liar to the species. 



In the male there are, on the left side of the abdomen, three 

 unpaired pleopods of the usual aspect, and in the female, four. 



The uropods are of the usual form. 



Ovigerous females have been taken on many occasions by 

 the Helga, most frequently in August and November, but also 

 in February and March, and there are ovigerous specimens 

 in the Irish National Museum from the same area wdiich were 

 taken in July. 



Size. — The carapace of the largest specimen taken by the 

 Helga is 19 mm. long. The females appear to become sexually 



