( n ) 



of last abdominal ring. Aceenwy lobe distinct, nearly attaining apex 

 of peduncle, unconcealed by last ring. Ischium — base flattened, apex 

 acuminate, bi- articulate, hairy, and spinod along edges. Accessory 

 appendage falciform, hairy, apex blunt, three-fourths of length of 

 ischium (Philoscia). 



5. Peduncle somewhat triangular, as long as broad, superior border 

 terminating internally in an angle, articulated in a notch of the posterior 

 linear border of the last ring, which passes back below coxa of fifth 

 ring. Exterior margin produced into a triangular lobe. Accessory 

 lobe triangular, distinct, nearly attaining apex of peduncle, uncon- 

 cealed. Ischium subulate, somewhat trigonal at base, terminating in 

 a long filament, smooth. Accessory appendage curved, needle-shaped, 

 smooth, nearly equal in length to ischium (Philougria, Itea (?), and 

 probably also Trichoniscus). 



6. Peduncle quinquangular, oblong, superior border narrow, articu- 

 lated in a distinct notch at the posterior margin of ring ; apex truncate; 

 exterior angle acute ; lateral lobe obsolete. Ischium elongated, trigo- 

 nal, rough, hairy. Accessory appendage rounded, subulate, slightly 

 larger than ischium, terminating in a filament (Ligia). 



Besides these there are several intermediate forms, as Ligidium, in 

 which the accessory lobe far exceeds apex of the peduncle — Actaecia 

 (Dana), in which the external angle of apex is produced into a lobe, so 

 that the ischium appears to be lateral ; but sufficient has been said 

 on the subject. 



The whole of these appendages are capable of reproduction, and it 

 is common to find Ligia with them in a rudimentary state. They 

 preserve their comparative characters, even in the young state of the 

 animals, the only difference being, that the accessory lobe is somewhat 

 more strongly marked, and afford the most valuable of all the characters 

 which I have mentioned, for fixity of a type. 

 The order of value of these characters is : — 

 Generic. 1st. Appendages of, and last ring of abdomen. 



2nd. Arrangement and form of external antennae. 

 3rd. Proportional development of coxa) of abdominal rings. 

 4th. Development of antenna! rings. 

 Familiar. 1st. Appendages of last ring of abdomen. 

 2nd. Proportional development of coxae. 

 3rd. Arrangement and form of external antennae. 

 The characters of the internal antennae and of the parts of the mas- 

 ticatory apparatus are chiefly of familiar import : they are so difficult to 

 i^eetablish that I have omitted them in this rough sketch, which is put 

 rard merely as an attempt at a more natural arrangement of these 

 ^iMnera than those published. It will be found that I have also omitted 

 81 mention of the internal anatomy for the present 



ICany of the foreign genera are so scantily described, that it would 

 be foolish to attempt anything like generalities here, and this whole 

 paper, as I said before, is merely provisional, the rather as I hope 

 before long to examine into, not merely genera, but species, as at pre- 

 sent far too many false ones incumber our systems. 



c 



