A FOSSIL’S KITH AND KIN 199 
CHAPTER XIV 
TRIBE IV.—ASTACIDEA 
THE first antenne carry two multiarticulate flagella; the 
second are furnished with a scale. The trunk-legs have 
seven distinct joints. The first three pairs of trunk-legs, 
and sometimes the other two pairs also, are chelate. The 
first pair are the largest. The branchiz are well developed. 
The first segment of the pleon has appendages, except in 
the Parastacide. 
In this tribe the young are said to be hatched in the 
Megalopa form. It contains four families—the Eryontide, 
Nephropsidze, Potamobiide, and Parastacidee. 
Family 1.—Eryontide. 
The carapace is dorsally depressed, with little or no 
rostrum. ‘lhe eyes are wanting or abnormal. The second 
antennz have a long multiarticulate flagellum. The third 
maxillipeds are pediform. The pleopods, exce, t the first 
pair, have a process attached to the inner branch (the 
stylamblys of Spence Bate’s terminology). The uropods 
~have no transverse suture. The telson is tapering. 
To this family are assigned seven genera, but one of 
these, Hryon, Desmarest, 1820, which gives its name to 
the family, is a fossil genus from the Lias of England and 
the lithographic limestone of Bavaria. It is only in re- 
cent years that: the depths of the ocean have yielded forms 
which appear to be properly classified in close proximity 
to the ancient fossil species. 
Polychéles, Heller, 1863, has the avterior angles of the 
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