PODOPHTHALMIA. 53 



in which the feet of the two posterior pairs are short and subdorsal, as 

 in Dromia; yet the essential characters are all Brachyural. De Haan 

 points out a relation between the Ranina group and Homarus among 

 the Macroura, mentioning a resemblance in the inner branch of the 

 first maxillipeds, which is narrow and elongate, and also in several 

 other characters.* 



From these facts with regard to the gradations of the species, it is 

 evident that we present a clearer view of the relations, if we keep the 

 Brachyural and Macroural groups distinct, each at its own level and 

 within its own circumscribed limits, and place the intermediate links 

 in a separate group, as proposed by Edwards. We may thus more 

 readily point out and exhibit these links and gradations. The mind 

 in its conceptions of the range and relations of the several groups, 

 imagining the interlinkings to take place among points in space, would 

 thus locate them. We^ therefore believe, that the group Anomoura 

 is established on philosophical grounds. Its diversities of types are 

 not greater than are found among the Brachyura, although more 

 striking as they occur among so small a number of species. 



Some interesting points will be developed on a farther considera- 

 tion of the subject. 



We have found that the Maioidea are connected with the Macroura 

 through three distinct grades of degradation, following Oncinopus and 

 Trichia, i. e., the Dromioid, the Lithodioid, and the Paguroid. Below 

 the Corystoidea we distinguish but one grade. Again, below the Grap- 

 soidea, we find but one (Porcellana) until we reach Galathaea, just on 

 the confines of the Macroura. The greater number of distinct grada- 

 tions between the Maia and Macroural type is a consequence, evi- 

 dently, of the high pre-eminence of the Maia type. Counting Parthe- 

 nopinea, and Oncinopus, as two proper grades in the descent, we may 

 distinguish five in all. From the Cancroids (ranging in the same 

 grade nearly with Parthenopinea), we pass to the Corystoidea, which 

 is a longer step than from Maia to Parthenopiuea; and thence to 

 Hippidea, which ranges at a lower level than Dromia, and a little above 

 Pagurus. From Grapsoidea, still lower than Cancroidea, we pass to 

 Porcellana, nearly on the same level with Hippa, and thence to Gala- 

 thaea, but just above the Macroura. I have attempted to represent 

 this relative grade by the relative level or % height in the following- 

 table ; and, although a rude representation of nature, it gives some 



* Crust. Faun. Japon. ; p. vii. 

 14 



