SÜBCLASS II 



EUCRUSTACEA— OSTRACODA 



735 



Family 2. Bradoriidae Matthew. 



Garapace bivalved, memhranaceous^ calcareo-corneus in composüio^i, not completely 

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

 slightly gaping ; main muscle spot dose to antero-cardinal angle just hehind and beneath 

 the ocular tuhercle. 



The niembers 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 subtriangiilar with a broad 

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



Fig. 1421. 



A, Beyrichona tinea Jfatthew. x Vi- -ß' 

 Beyrichona papilio Matthew. x ■^/i. Middle 

 Cambrian of New Brunswick. 



Fig. 1422. 



A, Hipponicharion clavatum Matthew. 



X 4/i- -B, ^luta enyo (Walcott). 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. 



Polyphyma Groom. Valves semicircular with numerous rather variable tubercules. 

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



Order 4. CLADOCERA Müne Edwards. 



Garapace hivalved, generally enclosing hody hut leaving headfree ; paired eyes sessile, 

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

 furcal rami claw-like. 



The egg-cases (ephippia) of Cladocera have been recognised in Glacial deposits 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 ahsent. Antennules anU 

 antennae usually well developed ; typicalhj six pairs of biramons body-limhs. Caudal 

 furca present. 



The Copepoda are without knovvn representatives in the fossil State. 



Superorder 3. OSTRACODA Latreille.i 



Small, indistinctly segmented Crustacea completely enclosed in a horuy or calcareoiis 

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



^ Literature : Bosquet, J., Description des Eutoniostraces fossiles de la craie de Maestrich t. 



