Ortmann — Crangopsis vermiformis. 289 



affinity with the Decapods. Pygocephalus may belong to the 

 "Schizopods"* in the old sense, which comprise the Euphau- 

 siacea and Mysidacea of recent systems, but we are at a loss to 

 say to which of the two latter orders it may be referred. 



In conclusion I may add that no Palaeozoic Crustacean is 

 known in which Decapod-characters have been observed. f 

 The only genus Anthrapalamion% of the Coal Measures of 

 Scotland and Illinois, which has been referred to the Decapods 

 from the appearance of the external form of the body, has 

 incompletely preserved legs, so that its true position remains 

 doubtful. It may be well to remember that true Decapods, 

 i. e. Crustaceans in which typical Decapod-characters are evi- 

 dent, are not found until the Triassic period, and that it may 

 be possible that they did not exist at all in Palaeozoic times. 

 On the other hand, it is sure that upwards from the Upper 

 Devonian period, through the Subcarboniferous, Carboniferous 

 and Permian, Malacostraca have been found, which represent 

 either a mere collective type of this subclass or show even 

 some tendency to become more specialized : at least a differen- 

 tiation of Thoracostraca and Arthrostraca took place probably 

 in the earliest Subcarboniferous or Upper Devonian period. 

 Remains of this primitive group, which may be conveniently 

 called Syncarida (Packard), have not yet been found in Meso- 

 zoic or Tertiary strata, but this group is still represented by 

 the genus Anaspides, living iti fresh water on the mountains 

 of Tasmania. 



Princeton University, January, 1897. 



* Huxley unites the Schizopods with the Decapods, and, accordingly, he calls 

 Pygocephalus a Decapod: but he expressly states its nearer relation to "Mysis," 

 a Schizopod. 



f Even an alleged abdomen of a Brachyurous Decapod, Brachypyge carbonis, 

 has been described from the Coal Measures of Belgium (Woodward, Geol. Magaz , 

 3 878, p. 433, pi. 11, and de Kouinck, Bull. Acad. Roy. Belg. (2), lxv, 1878, p. 83, 

 figs. 1, 2). It is extremely unintelligible why this fossil should belong to a Crus- 

 tacean at all, and whoever has seen the abdomen of a living crab, cannot doubt 

 that this fossil is no such thing. Probably Brachypyge belongs to the Arach.- 

 noidea (compare the Carboniferous Anthracomarti). 



X Salter, Quart. Journ. Geol. Soc , London, xvii, 1861, p. 529. figs. 1-7. Meek 

 and Worthen, Geol. Surv. 111., ii, 1866, p. 407, pi. 32, fig. 4, and iii, 1868, p. 554. 

 Etheridge, Quart. Journ. Geol. Soc, London, xxxv, 1879, p. 404, pi. 23. 



Am. Jour. Sci.— Fourth Series, Yol. IV, No. 22.— Oct., 1897. 

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