NO. 5.] ACCOUNT OF THE SPECIES. 31 



7. Pseudalibrotus glacialis, n. sp. 

 (PL VI). 



Specific Characters. Body somewhat less robust than in the preceding 

 species, and more compressed, with the back evenly rounded. Cephalon with 

 the lateral lobes distinctly angular at the tip ; eyes oval, with the visual elements 

 sometimes distinct, at others imperfectly developed. Anterior pairs of coxal plates 

 deeper than the corresponding segments; 1st pair rather broad and expanded, 

 with the antero-lateral corner rounded off; 5th pair more than twice as large 

 as the last. The 2 posterior pairs of epimeral plates of metasome acut- 

 angular behind. Urosome slightly depressed at the base dorsally. Antennae 

 comparatively shorter than in the preceding species, scarcely exceeding half 

 the length of the mesosome, flagella of both pairs composed of a smaller number 

 of articulations, accessory appendage of the superior ones 3-articulate. Anterior 

 gnathopoda about as in the preceding species; posterior ones, however, 

 differing in the propodos being obliquely truncated at the tip, with the lower 

 corner produced, so as to form, with the extremely small dactylus, a minute 

 chela. The 3 posterior pairs of pereiopoda somewhat less robust than in 

 the preceding species, with the terminal part more produced ; last pair scarcely 

 shorter than the preceding pair, with the basal joint rather broad in proportion 

 to its length, and but little longer than the terminal part. Last pair of 

 uropoda comparatively short, not projecting beyond the others, inner ramus 

 considerably shorter than the outer, with only a single denticle inside, both 

 rami without any marginal setae. Telson rounded quadrangular in form, and 

 but very slightly narrowed distally, terminal edge scarcely at all insinuated. 

 Length about 9 mm. 



Remarks. This species is nearly related to the preceding one, but is of 

 much smaller size, and moreover easily distinguished by the different form of 

 the anterior pair of coxal plates, the much shorter antennae, and the less 

 shortened terminal part of the last pair of pereiopoda. The posterior 

 gnathopoda, too, terminate in a somewhat different manner, and the structure 

 of the last pair of uropoda and of the telson is also somewhat different. In all 

 these characters, it approaches still nearer to the Caspian species, P. caspius 

 (Grimm), and in my opinion, it ought, indeed, to be regarded as the primitive 

 form, from which this species has descended. Yet on a closer comparison, 



