PTYCHOPARIA. 45 



THE APPENDAGES OF PTYCHOPARIA. 



Ptychoparia striata (Emmrich). 

 Illustrated : Jaekel, Zeits. d. d. geol. Gesell., 1901, vol. 53, part I, pis. 4, 5. 



Jaekel has described a specimen of this species obtained from the Middle Cambrian near 

 Tejrovic, Bohemia, which on development showed beneath the test of the axial lobe, cer- 

 tain structures which he believed represented the casts of proximal segments of appendages. 

 On the basis of this specimen he produced a new restoration of the ventral surface of the 

 trilobite, in which he showed three short wide segments in the place occupied by the coxopo- 

 dite of an appendage of Triarthrus. He also made the mouth parts considerably differ- 

 ent from those of the latter genus. Beecher (1902) showed that the structures which 

 Jaekel took for segments of appendages were really the fillings between stiffening plates 

 of chitin on the ventral membrane, and demonstrated the fact that similar structures ex- 

 isted in Triarthrus. It cannot be said, therefore, that any appendages are really known 

 in Ptychoparia striata, but some knowledge of the internal anatomy of the species is sup- 

 plied by the specimen. 



Ptychoparia cordillerae (Rominger). 



Illustrated: Walcott, Smithson. Misc. Coll., vol. 57, 1912, p. 192, pi. 24, fig. 2; Ibid., vol. 67, 1918, pi. 



21, figs. 3-5 (corrected figure). 



Walcott has figured a single individual of this species showing appendages, the accom- 

 panying description being as follows (1918, p. 144) : 



Ventral appendages. Only one specimen has been found showing the thoracic limbs. This indicates very 

 clearly the general character of the exopodite and that it is situated above the endopodite, although there are 

 only imperfect traces of the latter. . . . 



The exopodites are unlike those of any trilobite now known. They are long, rather broad lobes extending 

 from the line of the union of the mesosternites and the pleurosternites. At the proximal end they appear to 

 be as wide as the axial lobe of each segment, and to increase in width and slightly overlap each other nearly 

 out to the distal extremity. . . . They are finely crenulated along both the anterior and dorsal margins, 

 which indicates the presence of fine setae. 



The specimen is quite imperfectly preserved, but seems to indicate that the exopodite 

 of Ptyclwparia had a long, rather narrow unsegmented shaft. 



Measurements (from Walcott's figure) : The specimen is a small one, about 9.5 mm. 

 long, an individual exopodite is about 2 mm. long and the shaft 0.33 mm. wide. 



Horizon and locality: Middle Cambrian, Burgess shale, between Mount Field and 

 Wapta Peak, above Field, British Columbia. 



Ptychoparia permulta Walcott. 



Illustrated: Walcott, Smithson. Misc. Coll., vol. 67, 1918, p. 145, pi. 21, figs, i, 2. 



Walcott figured one individual of this species showing long slender antennules pro- 

 jecting in front of the cephalon. It is of especial interest because one of the antennules 

 shows almost exactly the same sigmoid curvature which is so characteristic of the related 

 Triarthrus. The individual segments are not visible. 



Measurements: The specimen is 23 mm. long and the direct distance from the front 

 of the head to the anterior end of the more perfect antennule is 9.5 mm. Measured along 

 the curvature, the same antennule is about 1 1 mm. long. 



Horizon and locality: Same as the preceding. 



