638 



MR. E. J. MIEES ON THE 



Fara. i. Maiid^e. Eyes retractile into orbrts. 



Fam. ii. Tychid.e. Eyes retractile beneath carapace ; no orbits. 



Fam. iii. Eurypodid^. Eyes retractile to sides of carapace. 



Fam. iv. Leptopodid.^;. Eyes not retractile. Legs very long. 



Fam. V. PERiCERiDiE. Byes not retractile. Legs of moderate length. 



"With respect to this arrangement I may observe, in the first 

 place, that the retractility or non-retractility of the eyes is scarcely 

 a character that can be used for separating the families ; for in 

 many of the Leptopodiidae the eyes are capable of a certain 

 degree of mobility, and in many Periceridae they are, as Stimpson 

 has pointed out, completely retractile within the orbital cavity. 

 It is somewhat remarkable that Dana did not observe the cha- 

 racters that are aff'orded by the structure of the orbital region 

 itself, taken in conjunction with the concurrent modification of 

 the form of the basal antennal joint, to which attention had already 

 been drawn by Milne-Edwards, and which, I am convinced, off"er 

 far better distinctions for a natural arrangement of the various 

 groups. "Within his first family (Maiidse) Dana includes most of 

 the genera referred by me to the Maiidoe and Periceridso ; his 

 second family (Tychidae) contains but three genera, whereof the 

 last, Camposeia, has but little affinity with the two preceding ; 

 the third (EurypodidsB) also includes but three genera, all refer- 

 able to my family Inachidaj ; the fourth (Leptopodidoe) cor- 

 responds, witli the exception of InaeJioides, to my subfamily 

 Leptopodiinse. The fifth (Periceridse) is a somewhat heterogeneous 

 group ; but the majority of the genera included in it belong to my 

 subfamily Acanthonychinse of the family Inacliidse. 



The subfamilies of the Maiinea instituted by Dana ap)pear to 

 me to be unnecessarily numerous, and are for the most part 

 founded upon characters of minor importance, i. e. the form of 

 the carapace and rostrum. His minor subdivisions, indeed, are 

 less natural than those of Milne-Edwards ; but to him belongs the 

 merit of having recognized that the Partlienopinea form a grouj:) 

 equal in value to the remainder of the Oxyrliyncha (with the 

 single exception of Oncinopus). 



M. Alplionse Milne-Ed wards, by whose finely illustrated memoirs 

 our knowledge of the genera of OAyrliyncha has been so greatly 

 increased, has not, I believe, published any classification of the 

 group; but in his classification of t1ie Brachyura set forth in the 

 introductory portion of his ' Histoire naturelle des Orustace.^ 



