488 NEW YORK STATE MUSEUM 



the carapace are very rare in the Pinon range material, only one specimen 

 having been observed [reproduced in text fig. 475]. 



That the larger bodies considered by Gurley as the detached lateral 

 appendages of the graptolite are true carapaces, is abundantly shown by 

 their outline 1 and by numerous specimens, compressed in dorso-ventral or 

 oblique direction. In these latter states of preservation the composition of 

 the carapace of two equal sides, folded upon each other and united along 

 the dorsal line (either by coalescence or by hinge) and the gaping of the 

 ventral part can be distinctly seen [see fig. 472 and 474]. 



The exclusion of Caryocaris from the graptolites does not directly 

 affect the position of Dawsonia among the latter. 



1 The normal outline of the carapace is seen in the specimen reproduced in text 

 figure 472. The dorsal margin makes a somewhat abrupt turn near both the anterior and 

 posterior extremities and the carapace may have been gaping there a little [see also anterior 

 extremity of text fig. 473]. The anterior extremity possessed two acute mucros [see text 

 fig. 472, 473], suggestive of Elymocaris cap sella and Tropidocaris bicarinata 

 and of other phyllocarids. The ventral margins show well the thickening by raised rims, 

 mentioned by Jones and Woodward. The posterior margin is straight, truncate and 

 vertical, without any trace of thickened rim, but provided with a fringe which is due to 

 the " plaiting " or imperfect cleavage of the shale. The dorsal margin in the laterally com- 

 pressed carapaces shows no trace of thickening or of a hinge or suture, but in obliquely 

 or dorso-ventrally compressed specimens [see text fig. 474, 477] a distinct, straight line of 

 the nature of a break appears in the exact location of the dorsal (median) line of the cara- 

 pace, running the greater length of the latter and suggesting a hinge line. On Gurley's 

 type of C. curvilatus [text fig. 477] this line is more prominent than any other and 

 ends anteriorly in a lancet-shaped process protruding from the carapace and correspond- 

 ing in form and position to the rostrum observed in the later phyllocarids. Altogether 

 one can not, in noting the additional features of the carapace here enumerated, fail to be 

 impressed with the greater similarity of this crustacean rather to such Devonian genera as 

 Elymocaris and Tropidocaris than to the older Hymenocaris. 



