SUBCLASS II 



EUCRUSTACEA— OSTRACODA 



735 



Family 2. Bradoriidae Matthew. 



Carapace bivalvcd, membranaceous, calcareo-corneus in composition, not completely 

 separated hut prohahly often fused along the cardinal edge; free margins of valves 

 slightly gaping ; main muscle spot close to antero-cardinal angle just behind and beneath 

 the ocular tubercle. 



The members of this family have hitherto been considered as Cambrian Ostracoda, but 

 recent studies have shown them to be Branchiopoda. The genera listed below embrace 

 several distinct types of structure, and will in part be referred to other families in the course 

 of study. 



Beyrichona Matthew (Fig. 1421, A, B). Valves subtriangular with a broad 

 undefined depression in the dorsal slope, limited in front by a short node-like ridge. 



A B 



Fig. 1421 

 A, Beyrichona tinea Jlatthew, 



Beyrichona papilio Matthew. 

 Cambrian of New Brunswick. 



X 4/i. B, 

 X •*/!. Middle 



Fig. 1422. 



A, Hipponicharion clavatiim Matthew. 

 X Vi- -B, Aluta enyo (VValcott). X 8/j. 

 Middle Cambrian of New Brunswick and 

 China. 



Hipponicharion Matthew (Fig. 1422, A). Valves semi-elliptical with two 

 prominent marginal ridges and an inconspicuous central ridge near hinge line. 



Pohjphyma Groom. Valves semicircular with numerous rather variable tubercules. 

 Bradoria, Escasona, Aluta Matthew (Fig. 1422, B). (?) Isoxys Walcott. 



Order 4. CLADOCERA Milne Edwards. 



Carapace bivalved, generally enclosing body but leaving head free; paired eyes sessile, 

 coalesced ; antennae large, forming swimming organs ; four to six pairs of body-limbs ; 

 f ureal rami claw-like. 



The egg-cases (ephippia) of Cladocera have been recognised in Glacial de2:)0sits in 

 Germany. Lynceites ornatus Goldenberg, from the Carboniferous, is a very doubtful 

 representative of this order. 



Superorder 2. COPEPODA Milne Edwards. 



Eucrustacea without a distinct carapace, but with one or two of the anterior 

 somites coalesced with the head. Paired eyes usually absent. Antennules and 

 antennae usually well developed ; typically six pairs of biramous body-limbs. Caudal 

 furca present. 



The Copepoda are without known representatives in the fossil state. 



Superorder 3. OSTRACODA Latreille.^ 



Small, indistinctly segmented Crustacea completely enclosed in a horny or calcareous 

 bivalve shell. Not more than seven pairs of appendages present — two of antennae, 



1 Literature : Bosquet, J., Description des Entomostraces fossiles de la craie de Maestricht. 



