REPORT OF THE DIRECTOR I919 99 



parallel with the superinduced grain of the schist, their ends are 

 frayed out or 'plaited' into a mere fringe." The writer (op. cit., 

 1908, p. 488) following suite, also attributed the " row of cilialike 

 processes " observed by both Gurley and himself at the posterior 

 margin of the carapaces ofC. curvilatus (see text figure 47) 

 to this " plaiting." The Alaska- Yukon material, however, which is 

 not obscured by an imperfect cleavage leaves no doubt that the 

 posterior margin of the carapace was indeed furnished with a fine 

 comb of uniform bristles or teeth corresponding to the " fringe " 

 observed in certain species of Ceratiocaris, as p. e. C. (L i m n o - 

 caris) salina Ruedemann (N. Y. State Museum Bui. 189, pi. 

 33, fig. 4, 5). 



Gurley's type specimen of C. curvilatus exhibits (see 

 text figure 38) a straight line projecting between the two partly 

 overlapping valves, that remained unexplained by Gurley, but was 

 suggested by the writer (op, cit., 1908, p. 488, footnote) to be 

 possibly of the nature of a rostrum. The specimen, here reproduced 

 in text figure 45 exhibits the true rostrum. It shows a distinct plate 

 in position, that is very sharply acute in front and rounded ovate 

 posteriorly and that can not be otherwise considered but as a rostrum. 

 The straight thick line along the dorsal margin may be only a rein- 

 forced edge rather than a median plate. 



No distinct eye-tubercles could be made out in the material at our 

 disposal. 



It may finally be noted that Zittel's Handbuch and Zittel-East- 

 man's textbook cite Caryocaris as a Cambrian genus according to the 

 former correlation of the Arenig flags. The Skiddaw graptolite 

 shales in Great Britain are, however, now known to be of Lower 

 Ordovician age and to correspond to the graptolite beds in Nevada, 

 Levis at Quebec and the Alaska- Yukon boundary which have 

 afforded the American specimens of Caryocaris. It is, hence, safe 

 to define Caryocaris properly as a Lower Ordovician or Canadian 

 genus, instead of a Cambrian one; as indeed has already been done 

 by Bassler in his invaluable Bibliographic Index. 



The form of the abdomen, telson and rostrum here described, leave 

 no doubt that Caryocaris is closely related and very similar to the 

 genus Ceratiocaris, that becomes so prominent in the later Ordovician 

 and Silurian periods. It still differs from the latter in the shape of 

 the carapace which is broader anteriorly and in the absence of an}'- 

 linear surface sculpture. 

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