60 PERMIAN FOSSILS. 
General Division ENtoMOSTRACA, Miller, 1785. 
This extensive section of the Crustacea comprises several orders of aquatic 
animals, chiefly of small size, and differing very greatly in their general appearance. 
The orders are arranged according to the structure of the maxillary and the prehensile 
apparatus, the characters of the pseudobranchiz, and the form of the tegumentary 
shell or cuirass. We may notice, as representatives, the genera Branchipus, Apus, 
Limnadia, Daphnia, Cyclops, Cypris, Cythere, Argulus, and Lernza. The Limulus has 
been placed by Latreille in this section; and according to Mr. Salter, the Trilobite 
belongs to a co-ordinate group." 
Up to the present time no researches of the palzontologist have proved the 
existence, durmg the Permian epoch, of other forms of Crustacea than those 
belonging to this division; two genera only, Cythere, Miller, and Dithyrocaris, 
Scouler, have been found in the Magnesian Limestone. 
Legion BRANCHIOPODA, Latreille. 
Order OsTRACODA, Latreille.” 
Genus Cythere, Miller. 
Synonyms. Monocutus, duet. prior. 
CytHeRE, Miller, 1785. 
CytHEriIna, Lamk., 1818. 
A marine Entomostracous Crustacean. Body of animal inclosed in a bivalve 
carapace ; animal, creeping; provided with three pairs of feet, all protruding from the 
shell. 
In the ‘ Monograph of the Entomostraca of the Cretaceous Formation,’ where we have 
entered more fully into the characters of the Ostracoda, we have subdivided the genus 
Cythere, Miller, into four groups, viz. Cythere proper, Cythereis, nob., Bairdia, M*Coy, 
and Cytherella, nob., characterised by the form of the carapace and the structure of 
its hinge. The absence of perfect valves sufficiently free from the matrix to be easily 
examined, renders it impossible to be quite decided in the arrangement of the ten 
Permian species of Cythere into their respective sub-genera. But taking the general 
form asa guide, we have considered Nos. 1, 3, 4, and 5as belonging to Cythere proper, 
Nos. 2, 6, and 9 to Bairdia, No. 7 as a Cythereis, and Nos. 8 and 10 as Cytherelle. 
These Entomostraca occur in considerable numbers in the Limestone from Byers’ 
Quarry, referred to at page 16, both in relief on the weather-worn surface of the 
! Geolog. Survey, 2d Decade. 
2 See Jones, Monog. Entom. Cret. Form., p. 7. 
