CANCROIDEA. 267 



Length of carapax, three and a half lines; breadth, the same; 

 length of hand, five and a half lines ; of moveable finger, two and a 

 half lines ; of arm, three and one-fourth lines. The post-orbital angle 

 is very short acute. The teeth or spinules of the front are very 

 nearly equally spaced, the interval between the two middle being a 

 little the deepest. The lower finger has the apex incurved and acute. 

 The seven teeth of the arm are acute spines, equally spaced. The 

 eyes have very short peduncles, and project hardly -es much as their 

 diameter. The spine at inner angle of orbit below, projects forward 

 nearly as far as the median teeth of the front, and is similar in form. 



FAMILY IV. PORTUNID^l. 



THE genera of Portunidae, through the description of supposed new 

 types and the subdivision of old genera, have been greatly increased 

 in number beyond those published in the work by Milne Edwards. 

 But some of these supposed new types are of doubtful merit, and the 

 subdivisions in part objectionable. Of the latter, some have been in- 

 troduced by De Haan, in following out his system of basing distinc- 

 tions upon the maxillipeds. The difficulties of such a mode of cha- 

 racterizing or arranging genera, have been illustrated by reference to 

 some of the Portunidse, on pages 73, 74. Some of the genera, how- 

 ever, are well sustained. We refer to the pages mentioned for re- 

 marks on these genera, and continue here with a few additional obser- 

 vations. 



The mouth organs, when their transitions are studied, scarcely 

 afford satisfactory characters for separating either the Lupa tranqueba- 

 rica or the hexagonal Lupas, from the rest. Yet there are other cha- 

 racters of importance, that sustain us in recognising each of these as 

 distinct groups. The Lupa tranquebarica has a large massy hand, 

 narrow above, and with bulging sides, not costate ; while in the other 

 Lupas, the hand has a trigonal or prismatic form, being strongly 

 costate longitudinally. Moreover, in this species, the epistome is dis- 

 tinct across, posterior to the bases of the antennae, while in other 

 species, it is obsolete except in its medial portion. 



