Scientific Inteligence. .120 
tains only two genera, Callianidea, Edw., and Isea, Guerin: the last 
name was changed by Edwards to Callianisea ; but as this word is so 
near Callianassa and Callianidea, a contraction to Callisea would be 
preferable. 
Subtribe 9. Astacidea.-—ln this subtribe we adopt De Haan's sec- 
tions, except that we exclude the Megalopidea, and we do not associate 
the Thalassinidea with the Astacidea. The sections or families are 
Scyllaride, Palinuride, Eryonide, and Astacida. 
Leach in 1819 subdivided the old genus Astacus, naming the marine 
species ( Homarus, Edw.) Astacus, and the fresh water (Astacus, Edw.) 
Potamobius. Eid wards's division, of like character, now generally ac- 
cepted, was not published till 1837. Leach hence has the priority. 
But according to Leach, the name Astacus is appropriated, not to the 
typical part of the group, that including the Astacus fluviatilis of old 
authors, or Cancer Astacus of Linns;eus, and which embraces at the 
present time numerous species, but to that including the Cancer Gam- 
marus of Linnsus, still but a small group. There is hence much ob- 
jection to the names of Leach, and morever much confusion would 
now ensue from their adoption. "There seems, therefore, to be suffi- 
cient reason for rejecting them, if it be of no weight that they have 
remained for 30 years unrecognized by British authors. "They are 
adopted in the Catalogue of Eritish Crustacea of the British Museum, 
published in 1850, but not in the general Catalogue of 1847. 
 Subtribe 3. Caridea.—ln arranging the Caridea ipto groups, much 
stress is usually laid upon external form and length of beak. "T'he un- 
importance of these characters is inferrible from the fact that they in- 
volve no essential variations of structure. Moreover, in a single natu- 
ral group, we may find both the long and short beak. In the Crangon 
group, for instance, in which the beak is usually very short and the 
body depressed, we have a species with the beak and habit of an 
Hyppolyte. 
'There are other characters of more fundamental value ; and these 
have been brought forward by De Haan. "The mandibles afford the 
distinctions alluded to. In one section they are very slender and are 
bent nearly at a right angle, without enlargement at the crown. In 
another they are very stout, and somewhat bent above with a broad di- 
lated crown. In a third, they are stout, but not bent, and have a 
dentate summit. In a fourth they have, in addition to a projecting 
lateral crown, a large summit process, which is often oblong and very 
prominent. "These forms are characteristic of different sections of the 
Caridea. 
'The fact that the mandibles bear a palpus or not is of much less im- 
portance ; for the portion of the mandible which is most essential to its 
functions is the crown.* Among the Palzmoninz, there are genera 
having a mandipular palpus, and others without one ; while the two 
kinds in other respects are remarkably close in their relations. We 
have found moreover, that in this group, the length of the palpus va- 
ries with the disjunction of the 2d and 3d flagella of the inner antennz. 
If these flagella are separate to their bases nearly, (as in Palzemon,) 
* The highest Crustacea have no manibular palpi. 
