16 Mr. E. J. Miers on new or little-known 



genus. Basal antennal joint not dentated, or with a single 

 small tooth on its anterior margin. Anterior legs (in the 

 female) small and weak. Ambulatory legs smooth, without 

 tubercles or spines. Postabdominal segments (in the female) 

 distinct. Length of carapace about § inch, breadth between 

 the third and fourth lateral marginal spines § inch. 



Hah. West Indies (Scrivener). 



There are in the British Museum the carapaces of two 

 individuals (sex unknown), which differ only in their some- 

 what greater proportional breadth. The length of the larger 

 individual is about 1 inch and ^ line, the breadth 11^ lines. 

 The colour of these carapaces is greenish upon a pale ground, 

 the green hue predominating on the anterior portion and form- 

 ing reticulations upon the back and sides of the carapace. 

 Traces of the same reticulations are visible on the sides of the 

 carapace in the typical specimens of 0. quadridentata. 



That all these examples belong to the same species can 

 scarcely be doubted ; the greater breadth of the carapace in 

 the two last-mentioned may be due to age or sex. This 

 species is distinguished from all its congeners by the non- 

 existence of the fifth and sixth lateral marginal spines, even 

 in a rudimentary condition. The smoothness of the carapace 

 further distinguishes it from all the species known, except 

 0. laevigata, A. M. -Edwards. These may appear but slight 

 diagnostic characters ; but this species is more distinct from 

 its nearest allies than 0. Lherminieri (for example) is from 

 0. laevigata or 0. sexdentata from either. There appears to 

 be no alternative between separating the species on such slight 

 differences and uniting all, both from the eastern and western 

 American coasts. 



Parathoe rotundata, gen. et sp. n. (PI. V. fig. 2.) 



Carapace subtriangular, rounded behind, and indistinctly 

 tuberculated ; the gastric and cardiac regions are distinctly 

 defined and nearly smooth ; there are four or five indistinct 

 rounded elevations on the branchial regions, and two tuber- 

 cles on the posterior margin. The rostrum is very small, 

 little prominent, and notched at its extremity. The anterior 

 legs (in the male) are robust ; arm and wrist smooth ; palm 

 enlarged, smooth and compressed; fingers arcuate, and meeting 

 only at the tips, which are excavated. On the inner margin 

 of the mobile finger, near its base, is a small tubercle. The 

 ambulatory legs are robust, with the merus joints strongly 

 tuberculated. The rather narrow basal antennal joint is un- 

 armed at its distal end. The postabdominal segments (in the 

 male and female) are smooth and distinct. Length 3^ lines. 



