678 ON A NEW CRUSTACEAN, 



being little broader than the head, the last nearly three times as 

 broad. There are some slight differences between different indi- 

 viduals in the form and size of the segments, but they are too 

 slight to require particularisation. In one female all the thoracic 

 segments are densely bordered laterally with long pinnate hairs, 

 in another hairs are almost entirely absent. The abdominal 

 segments, though short, are distinctly separated from one another; 

 the first and the last are larger than the others. The appendages 

 of the last segment are on a type similar to those of Anthura, 

 with a dorso-ventrally compressed peduncle, a ramus, which is 

 serrated and obtusely pointed ; and an appendage which is 

 directly articulated with the posterior border of the segment. 

 This appendage is a curved plate with a strong acute spine on its 

 distal border, which is minutely serrated. The telson is a broad, 

 somewhat quadrate structure with a serrated distal border. The 

 arrangement of these parts is such that the caudal appendages and 

 telson form an irregular shallow cup with the opening directed 

 towards the dorsal side, and this forms a very efficient operculum 

 for the closure of the tube. The abdominal appendages are very 

 much like those of Idotea, the first pair forming a pair of valves 

 closing over the rest, which are very delicate and membranaceous 

 All the thoracic appendages are very similar in character, none of 

 them being subchelate. The first three pairs are turned forwards, 

 the last four backwards ; the posterior are rather the smaller, and 

 have the spines less prominent, but otherwise there* is little 

 difference between them. The basal joint is narrow ovate, with a 

 deep excavation at its distal end. The ischium is of similar shape 

 but smaller, it bears externally a row of about twenty short 

 conical spines and on its internal border a few small hairs. The 

 meros is small, with four conical spines externally : the carpus is 

 still smaller than the meros, with a row of minute spinules and a 

 longer spine on its outer border. The propodos is longer than the 

 meros and carpus together, nearly parallel-sided, with an oblique 

 distal border : on its inner border is a row of minute spinules, 

 with at the angle a stouter spine ; towards the dorsal border are a 

 lew short spines. The dactylos is stout, with an acute accessory 

 spine near its apex. 



