some British Fossil Crustacea. 395 
a point, the inner edge being straight and simple, the outer edge 
slightly convex. The hands of both kinds of chelz are similarly 
sculptured with short, fine, sharp, irregularly curved, longitu- 
dinal plice, proving their identity, and that thus, like the recent 
Pecilopoda, more than one pair of feet were didactyle. 
In the fine olive schists (of the age of the Upper Ludlow 
rock) of Leintwardine. 
(Col. University of Cambridge.) 
Trib. Phyllopoda (= Branchiopoda, M. Edw.). 
This tribe might be divided into the five following families, 
all having membranous feet :— 
1, Daruntav# (= Cladocera). Carapace oval, compressed, the 
posterior portion bivalve, inclosing the body, the anterior end 
forming a separate beak-shaped hood for the head. ye sin- 
gle, semicompound*. eet, only four pair, foliaceous. An- 
tenne, first pair small; second pair very large, branched and 
bristled for swimming. (Type Daphnia, &c.) 
The Daphnia? primeva (M‘Coy), Syn. Carb. Foss. Irel. t. 23. 
f. 5, is the only probable example of this family I know in the 
fossil state. 
2. Brancuipopiapm®. Carapace none, all the body-rings di- 
stinct and naked. (Type Branchipus.) 
I know of no fossil example of this group. 
3. Tritopitap& (= Paleade). Head and abdomen covered by 
separate dorsal shields, thoracic segments naked, separately 
moveable, generally trilobed by two longitudinal depressions. 
Eyes two, large, semicompound, or absent. 
This very extensive group is only known in the fossil state, 
and apparently confined to the paleeozoic rocks. I will offer some 
observations of detail below. 
4. AvopiaAp&. Carapace a semi-oval, horizontal shield, not 
covering the abdominal segments, which are distinct. Eyes, 
one simple and two large semicompound ones. Feet, about 
60 pair. (Type Apus.) 
The carboniferous genus Dithyrocaris is I think referrible to 
this group, though I have not yet detected the eyes. (See Syn. 
Carb. Foss. Irel. t. 23. f. 2.) 
* TI use this term to particularize that type of eye so common among the 
Entomostraca, in which a mass of minute eyes are covered by one simple, 
undivided, external cornea, being thus intermediate between the simple eye, 
and the true compound eye in which the external cornea is faceted, and 
divided into as many portions as there are eyes beneath. 
