304 Transactions.—Zooloyy. 
those which possess the stridulating organ. A second very natural sub- 
division, but of less importance than the first, is indicated by the line c d 
which divides the stridulating species into brevicorn and longicorn forms. 
For systematic purposes it will probably be convenient to employ both 
these boundary lines, that is, to divide the species into three sub-genera 
instead of two as heretofore. The non- atridalabiog. species or Silentes form 
the first sub-genus, which I propose to call Jasus:* the stridulating forms 
or Stridentes fall into two sub-genera, one of brevicorn species, to which the 
name Palinurus may be restricted, and one of longicorn species, equivalent 
to Milne-Edwards's Langoustes longicornes, Gray's Panulirus, and Pfeiffer's 
Senex, 
Put in a tabular form the classification I propose is as follows :— 
Genus Palinurus, Fabr. 
A, SILENTES. Stridulating organ absent; rostrum well developed, clasped 
by paired pedate processes of the epimeral plates ; | procephalie pro- 
cesses present; coxocerites imperfectly fused ; antennulary flagella 
short. 
Sub-genus Jasus, T.J.P., 
Includes P. lalandii, P. edwardsii, and P. hiigelii 
B. Srawenres. Stridulating organ present; rostrum variable, but rarely 
(? never) as well developed as in A; pedate yerum processes 
absent; procephalie processes absent. 
a. Antennulary sternum narrow below and bases of antenne con- 
sequently approximated; bases of antennules hidden, in a 
view from above, partly by the antennulary sternum, partly 
by the antenne; coxocerites imperfectly fused ; antennulary 
flagella short. 
Sub-genus Palinurus, Fabr., in part. 
a. Rostrum well developed, covering ophthalmie segment. 
P. trigonus. 
B. Rostrum reduced to a small spiniform tubercle; oph- 
thalmie segment uncovered. - 
P. vulgaris: 
b. Antennulary sternum broad below, causing a wide separation 
of bases of antenne; bases of antennules visible in a view 
from above; rostrum absent; ophthalmie segment uncovered ; 
coxocerites perfectly fused; antennulary flagella long. 
Sub-genus Panulirus, Grey, Senex, Pfeiffer, 
Includes P. interruptus, P. japonicus, P. penicillatus, F. ornatus, ete. 
* Jasus, according to Lempriére, was the father of Palinurus. 
