16 



PROCEEDINGS OF THE NATIONAL MUSEUM 



VOL. 7y 



these same shell glands are also retained in peculiar cranidial de- 

 pressions of full-grown trilobites, as, for example, in the " lunettes '' 

 of Bwniastus. Anyone who has observed the prominent shell glands 

 in the carapace of an A'pus or noted their location in such other 

 primitive crustaceans as Branchipus and Daphnia (fig. 6) or the 

 prominent develoj^ment of the maxillary or shell glands in the lar- 

 val forms of the Branchiopoda, Ostracoda, Copepoda, and Cirri- 



pedia will expect to see shell 

 glands as a distinct feature in 

 the freshly molted trilobites and 

 will not be surprised to see their 

 markings retained on the inside 

 of the carapace of mature indi- 

 viduals. 



Plate 6, Figure 1, as well as 

 Plate 7, Figures 1 and 2, shows 

 clearly the torn and ragged pos- 

 terior (interior) edges of the 

 frontal "horns," which though considered appendages by Walcott 

 and Raymond, are in reality the frontal doublure of the cephalon. 



Occurrence. — Middle Cambrian, Burgess shale (Loc. 35K) , Burgess 

 Pass, near Field, British Columbia. 

 Plesiotypes.—IJ.^.'EM. No. 83486. 



FiGUEE 6. — Daphnia longispina O. P. Miiller 

 Frontal view. (After Woltereck) 



BIBLIOGRAPHY 

 Chapman, F. 



1919. New or little-known Victorian fossils in the National Museum. Pt. 

 23, On some hydroid remains of Lower Paleozoic Age near Mone- 

 getta, near Laucefield. Proc. Roy. Soc. Victoria, new ser., vol. 31, 

 pt. 2, pp. 388-393 

 Enqleb, a., and Pbantl, K. 



1897. Die natiirlichen Pflauzenfamilien. I. Teil. Abt. 2, Euthallophyta. 580 

 pp., 288 figs. Leipzig. 

 Fedotov, O. 



1925. On the relations among the crustaceans, trilobites, Merostomata, and 



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 Henbicksen, K. L. 



1928. Critical notes upon some Cambrian arthropods described by Charles 

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 pp. 281-282, 1929. 



PlA, JUUUS. 



1926. Pflanzen als Gesteinsbildner. Gebr. Borntrager, 255 pp. Berlin. 



1927. Die Erhaltung der fossilen Pflanzen. Hirmer, Palaobotanik, Bd. 1, 



136 pp. 

 Paekeb, J. J., and Haswell, W. A. 



1910. A textbook of zoology, vol. 1, 839 pp., 704 figs. London. 



