EU11YDICE PTJLCHRA. 311 



THIS beautiful little species was first described and 

 figured by Slabber, in bis fine microscopical work, 

 above referred to. His article on it lias, however, been 

 overlooked by all carcinologists, except Van Beneden, 

 who has published a detailed account of it in his re- 

 searches on the littoral fauna of Belgium, and who 

 remarks that no naturalist had reobserved Slabber's 

 animal; this is not indeed surprising, since the de- 

 scription of it by Leach (which has hitherto served for 

 all subsequent writers on this tribe) is so short and 

 unsatisfactory as not to be readily recognized. 



The body is smooth and of a pale grey colour, each 

 segment marked with about eight or ten black dots 

 formed of delicate radiating lines, closely resembling the 

 markings upon certain varieties of agate ; these spots 

 are arranged transversely and with a great amount of 

 regularity upon the succeeding segments ; each of the 

 basal joints of the tail, on the other hand, is marked with 

 two transverse spots formed of a series of very fine 

 black lines ; the large terminal segment is transversely 

 depressed near the base ; the tail is furnished on its 

 underside with five pairs of foliaceous membranous plates, 

 each articulated across the middle, the basal division 

 being almost square, and the apical division nearly semi- 

 circular, the latter fringed all round with about twenty- 

 five very fine hairs, each of which is fringed along its 

 whole length with most delicate cilia ; the outer pair of 

 the caudal plates do not perform the duty of an opercu- 

 lum as in the Idotese, and the sides of the terminal 

 segment are furnished with lateral appendages, the outer 

 division of each of which is smaller than the inner por- 

 tion, which is obliquely truncate at its extremity, and 

 hatchet-shaped. 



This species is found in small pools left by the re- 



