GRAPSOIDEA. 309 



Fam. V. Pinnotiiefjdjl — Oculi perbreves, orbitis insiti, raro non re- 

 tractiles. Carapax sive obesus, sive depressus, raro paulo oblongus 

 et interdum parce rostratus, lateribus valde rotundatis. Antennae 

 internae aut transversae aut obliquae. Abdomen maris angustum, 

 versus basin sterno contiguo valde angustius. Palatum colliculo 

 viae efterentis limite instructum. (Species omnes parvae.) 



Fam. VI. Myctiridae. — Corpus obesum. Carapax antice perangustus, 

 vix rostratus, orbitis carentes. Antennae internae parvulae, longi- 

 tudinales. 



We do not believe in a properly lineal order in classification ; yet 

 the succession we have given to the families is a natural succession, as 

 nearly as can be made. The first, Gonoplacidae, link the Grapsoidea 

 with the Cancroidca, and the genus Eucrate is very near Eriphia and 

 Panopaeus in form. The second, Macrophthalmidae, is closely allied 

 to the first, so much so that Macrophthalmus and Gonoplax have been 

 arranged in the same group. The third, Grapsidae, are again very 

 near the Macrophthalmidae, and the genus Helice is almost as cor- 

 rectly placed with one as the other. Thence the transition is as 

 gradual also, to tbe fourth or Gecarcinidae, and from the fourth to the 

 fifth or Pinnotherida, and from the fifth to the sixth or Myctiridae. 

 Still, there are other relations of somewhat less prominence, which 

 this order does not exhibit. The Myctiridae are evidently an aber- 

 rant form, of inferior grade, intermediate between Pinnothera, Doto 

 (or Ocypoda), and Heloecius. The resemblance of Elamena to Ina- 

 chus was long since recognised. 



The Gonoplacidae are placed in the Cancer group by De Haan, who 

 neglected the important distinction based on the male verges. The 

 other genera, exclusive of Pinnothera and the species related, he 

 divides into two groups, the Ocypus and Grapsas groups, the former 

 having the fourth joint of the outer maxillipccls articulated with the 

 outer angle of the third, and the latter, articulated with the middle of 

 the apical margin, — a distinction difficult to carry out and dividing 

 natural groups, as the Gecarcinidae, Grapsidae, &c. His genera of the 

 OotpuS group, are Doto, Scopimera, Myctiris, Gelasimus, Macroph- 

 thalmus, Cleistostoma, Cardisoma, Chasmagnathus, Helice, Uca, Ocy- 

 poda, Acanthopus (a division of Plagusia) ; those of the GrapsuS 

 group, are Gecarcinus, Philyra (division of Plagusia), Plagusia (ano- 



78 



