136 G'enera of Gammaracea. 
tion, has the 4 anterior feet non-prehensile; but in his figures, these feet are sub- 
prehensile though minute, and they resemble in this, many .Amphitoe, Orchestic, and 
Allorchestes. "lhe two anterior feet of the Talitri vary widely, from an obsolescent 
hand to a large strong prehensile form. Here as elsewhere in nature, there is no 
saltus in the gradations to aid us in generic groupines. 
The larger part of the new genera recently added, have been instituted by Króyer 
from species obtained in high northern latitudes. It is remarkable that the forms in 
this tribe should be so greatly varied in the colder seas, and the genera so few in 
tropical latitudes. 
Faw.I. ORCHESTIDJE. 
1. Pedes secundi non subcheliformes. Antenne su- 
periores basi inferiorum breviores. Talitrus (Latreille). 
2. Pedes primi secundique subcheliformes. Antenna 
superiores basi inferiorum breviores. Maxillipedes ad 
apicem obtusi. Orchestia (Leach). 
3. Pedes primi secundique subcheliformes. Antennce 
superiores breviores, basi inferiorum longiores. Maxil- 
lipedes ad apicem unguiculati. Allorchestes (Dana.*) 
Fax.Il. GAMMARIDJZE. 
SUB-FAM. l. LYsIANASSIN E. 
Antenna superiores ad basin crasse. X Epimera grandia. Pedes sex 
postici non prehensiles. 
T. Pedes subcheliformes nulli, secundis interdum exceptis. 
a. Pedes quinti sexti septimique directione similes. 
l. Antenne superiores appendiculatze. Lysianassa (M. Edw.). 
2. Antenns superiores non appendiculatz. PhAlias (Guérin). 
b. Pedes quinti tertii quartique directione similes. 
l. Antenn: sup. appendiculate.  Palpus mandibula- 
ris l-articulatus. Stegocephalust (Króyer). 
II. Pedes primi subcheliformes, secundi non subcheliformes ; reliqui 
non prehensiles. 
1. Antenne sup. appendiculate. Opis] (Króyer). 
2, Antenn:z sup. non appendiculate. ^ Pedes secundi 
vergiformes ; tertii quartique brevissimi. Uristes (Dana). 
III. Pedes primi secundique subcheliformes, reliqui non prehensiles. 
l. Antenn:z sup. appendiculatze. -AnonjyzS (Króyer). 
2. Antennz sup. non appendieulatze. Stenia (Dana). 
* The species of this genus have the aspect of many Amphithoe, and have proba- 
bly been hitherto referred to that genus. They have the very short posterior stylets 
of the Orchestiz, and resemble them in habit and in the absence of a palpus to the 
mandible ; while they differ in having the superior antenne /ongest and in the stout 
&pine or claw terminating the maxillpeds. "The writer has dissected the mouth of 
nearly a dozen species of Allorchestes. 
1 Króyers Naturhistorisk Tidsskrift, (Copenhagen,) iv, 150, 1842. * Caput oculis, 
ut videtur, destitutum." * Antenne breves (capitis altitudine non longiores)" * Pedes 
quinti paris pedibus tertii quartique paris structurà et directione similes." 
I Tids.iv. 149. * Pedes primi paris chelis armati portentosze magnitudine. Re- 
liqua cum genere A70nyce fermé conveniunt." 
8 Tids, 1i, 256 and iv, 164. "This genus is united with Lysianassa by Milne Ed- 
wards. Any species wholly without hands are properly Lysianasse; those with 
only two anterior hands, however minute or imperfect, belong to Opis. 
