724 CAMBRIAN BRACHIOPODA. 



Superfamily CRANIACEA Waagen. 



Family CRANIID^ King. 



Genus PHILHEDBA Koken." 



Philhedm Koeen, 1889, Neues Jahrb. fiir Mineralogie, Beilage-Band 6, Hft. 3, p. 465. (Discussed in German as a 



new genus.) 

 Philhedra Koken, von Huenb, 1899, Neues Jakrb. fur Mineralogie, Bd. 1, pp. 146-147. (Described and discussed in 



German. See below for translation of diagnosis.) 

 Philhedra Koken, von Huene, 1899, Verhandl. Russ.-kais. min. Gesell. St. Petersburg, 2d ser., Bd. 36, Lief. 2, pp. 



216-218 (list of species referred to Philhedra), and pp. 297-298. (Described and discussed in German.) 

 Philhedra Koken, Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 4, PL XI, and pp. 142 and 147. (Classification 



of genus.) 



The emended diagnosis of the species by von Huene follows: 



Inequivalve, with the flat ventral shell attached. Dorsal shell subconical to bowl-shaped, frequently irregularly 

 bent; the concentric growth lines are mostly crossed by radial ribs or rows of prickles; without limbus. Anterior 

 occlusors larger than posterior occlusors. 



Type. — Patella rivulosa Kutorga. 



Von Huene, in his memoir on the Silurian Craniidae [1899b, pp. 181-359], redefines the genus 

 Philhedra of Koken, and considers P. columbiana (Walcott) as its oldest representative. The 

 student who wishes to pursue the study further should read von Huene's memoir on the SHurian 

 Cramidse [1899b, pp. 181-359] and his "Systematik der Craniaden" [1899a, pp. 138-151]. 



Philhedra columbiana (Walcott). 



Plate LXXXI, figure 10. 



Crania? columbiana Walcott, 1889, Proc. U. S. Nat. Mus. for 1888, vol. 11, p. 441. (Described and discussed as a 



new species.) 

 Crania? columbiana Walcott, von Huene, 1899, Neues Jahrb. fiir Mineralogie, Bd. 1, p. 141, footnote. (Mentioned.) 

 Philhedra? columbiana (Walcott), von Huene, 1899, Verhandl. Russ.-kais. min. Gesell. St. Petersburg, 2d ser., Bd. 36, 



Lief. 2, pp. 216 and 298. (Mentioned.) 

 Crania columbiana Walcott, Matthew, 1902, Trans. Roy. Soc. Canada for 1902, 2d ser., vol. 8, sec. 4, No. 3, pp. 108-109. 



(Copies the original description, Walcott, 1889c, p. 441.) 

 Philhedra columbiana Walcott, 1908, Canadian Alpine Jom-n., vol. 1, No. 2, PL I, figs. 5 and 5a. (No text reference. 



Figs. 5 and 5a are copied in this monograph, PL LXXXI, figs. 10 and 10', respectively.) 



Shell small, subcircular, or a little longer than wide, subconical with the apex slightly 

 eccentric. Outer surface exfoliated; the inner layer of the shell appears to have been com- 

 posed of a calcareocorneous substance; it is marked by from 40 to 45 fine ribs that radiate 

 from the apex to the margin. Diameter about 2 mm. When preparing this monograph I 

 carefully examined the original specimen, removed a little of the attached matrix from the 

 outer margins and discovered traces of what appear to be minute spines radiating from the 

 margin. 



Many collections from the type locality of this species have passed through my hands 

 from 1888 to 1906, but it was not until the summer of 1907 that another specimen was seen, 

 and then only two were found in the Ogygopsis zone of Mount Stephen. These are both crushed 

 and broken specimens of the inner side of the conical valve. There is a strildng similarity 

 in appearance between this shell and Crania Ixlia Hall and Clarke [1892c, PI. IV h, fig. 1] and 

 other similar forms. 



The specific name is derived from British Columbia. 



Formation and locality. — Middle Cambrian: (14s) About 2,300 feet (701 m.) above the Lower Cambrian and 

 2,700 feet (823 m.) below the Upper Cambrian, in the Ogygopsis zone of the Stephen formation [Walcott, 1908f, p. 210], 

 on the northwest slope of Mount Stephen, above Field on the Canadian Pacific Railway, British Columbia, Canada. 



a The synonymy for this genus is not complete and does not even give a record of all the genera mider which the Cambrian species of Philhedra 

 has been placed; it gives only those references in which the genus is discussed or described. To complete the record for the species taken up in 

 this monograph tlie following mere references are listed: 



Crania ? Walcott [18S9c, p. 441]. | Crania Matthew [1902c, p. 108]. 



Crania? von Huene tl899a, p. 141]. I 



