NO. 5.] ACCOUNT OF THE SPECIES. 31 



7. Pseudalibrotus glacialis, n. sp. 

 (PI. 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 comer 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 obHquely 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, 



