34 



The Ottawa Naturalist 



[May 



iorly than in the other two species. They are all 

 large-eyed Phacopinids with the characteristic modi- 

 fications of the subfamily. The diagnostic feature 

 that separates this group from the coeval Silurian 

 Phacops forms is the retention of the first pair of 

 glabella furrows which are of a characteristic form 

 and give rise to a partly detached frontal lobe some- 

 what as in Dalmaniies. 



Genolype : Phacops gloc^eri Barrande. 

 Genus Phacops Emmrich s. str. 



1819. Somalrilfelon McMurtie, Sketches of Louis- 

 ville and the falls of the Ohio ; Louisville, 

 1819, pp. 74-75 (not sufficiently defined to 

 be clearly recognizable). 



1839. Phacops Emmrich (partim), De Trilob. 

 Dissert., p. 18. 



1843. Phacops Goldfuss (partim), Neues Jahr. 

 Min., etc., 1843, p. 564. 



1845. Phacops Emmrich (partim), Neues Jahr. 

 Min., etc., 1845, p. 38. 



1846. Portlockia McCoy (partim), Sil. Fossils 

 Ireland, p. 50. 



1852. Phaccps Barrande (partim), Syst. Sil. du 



Centre Bcheme, 1 , p. 498. 

 1864. Phacops Salter (partim), Mon. Brit. Tril., 



Pal. Sec, p. 14. 

 1888. P'hacops Hall, Pal. N.Y., 7, p. XXVH. 

 1905. Phacops {^^Somalri]felon) Reed, Geol. 



Mag., (5), 2, pp. 226, 228. 

 1911. Phacops Wedekind (partim), Zeitsch. 



Deutsch. Geo.. Ges., vol. 63, p. 317. 

 1913. Phacops Raymond, Zittel-Eastman Textb. 



Pal., 2nd ed., p. 726. 



As here restricted and based upon the genotype, 

 the genus includes all of Phacops Wedekind with 

 the exception of the Silurian group of P. slokesii. 

 Although the author of Phacops did not choose a 

 genotype for it, P. laiifrous Bronn has been so de- 

 signated by Barrande. He practically selected it in 

 1852 defining the usage of Phacops by referring to 

 the type of P. latlfrons. 



The status of Somairikclon McMurtie requires 

 consideration, since, if established, as a synonym of 

 Phacops s. str., it would have priority. McMurtie 

 (1819) described a new genus and species, Soma- 

 trilielon megalomaion, from a specimen found in "a 

 block of limestone from the falls [of the Ohio]". 

 In the diagnosis given, it is said to have a corrugated 

 (segmented), tripartite, convex body, the axis arched, 

 with a row of tubercles on either side, and the head 

 subrotund with very large eyes. The "mouth" is 

 said to be "formed like that of a snapping turtle". 

 It may possibly have a tuberculose surface, for the 

 statement is made that there is "not the smallest 



tubercle or wrinkle but what is preserved in its 

 original form". The author must be referring to 

 something more than the tubercles at the extremities 

 of the axial thoracic segments or he would not make 

 use of the superlative. Only one specimen was 

 known. The tripartite and corrugated (segmented) 

 body suggests a trilobite. The large eyes point to 

 either a Proetus or a Phacops. Both are present 

 in the Devonian at the falls of the Ohio. The very 

 large eyes and the possibly tuberculose surface sug- 

 gests a Phacops. Three forms are found in the 

 vicinity. Phacops Tana Green occurs in the Jeffer- 

 sonville limestone and Sellersburg beds (Onondaga 

 and Hamilton).* P. cristaia Hall is in the Jeffer- 

 sonville limestone and just above the hydraulic beds 

 of the Hamilton,* while its var. pipa Hall is found 

 in the upper Onandaga.* They are all pronounc- 

 edly tuberculose, especially on the glabella. Indeed 

 if we were certain of this character, Somatrilfelon 

 megalomaion McMurtie could be identified as a 

 Phacops and as one of the three forms mentioned. 



Vogdes (1893, p. 163) has listed McMurtie's 

 species as a synonym of Phacops rana Green and 

 Reed (1905, p. 226) suggests the possible use of 

 Somatril^elon, but does not discard Phacops for it 

 (1905, p. 228). The evidence certainly does not 

 justify any decided conclusion. Therefore, since 

 McMurtie's description although suggesting a 

 Phacops is not at all conclusive, since only one 

 specimen ever existed and that apparently is now 

 lest, and as no one has adopted it although recog- 

 nized by Vogdes, the v/riter prefers to regard it 

 as having a doubtful status. As Vogdes observed 

 long ago the generic name is very unsuitable any- 

 way, rpplying as it does to the Trilobita as a whole. 



Genotype: Phacops laiifrons Brcnn. 



Subgenus Portlcckia McCoy emend. 



1839. Phaccps Emmrich (partim), De Trilob. 



Dissert., p. 18. 

 1843. Phacops Goldfuss (partim), Neues Jahr. 



Min., etc., 1843, p. 564. 



1845. Phacops Emmrich (partim), Neues Jahr. 

 Min., etc., 1845. p. 38. 



1846. Portlockia McCoy (Partim), Sil. Fossils 

 Ireland, p. 50. 



1852. Phacops Barrande (partim), Syst. Sil. du 



Centre Boheme, I , p. 498. 

 1864. Phacops Salter (partim), Mon. Brit. Tril., 



Pal. Soc, p. 14. 

 1906. Phacopidella Reed (partim), The Lower 



Palaeozoic Tril. Girvan, III, Pal. Soc, 



p. 154. 

 1911. Phacops Wedekind (partim), Zeitschr. 



Deutsch. Geol. Ges., vol 63, p. 317. 



*Personal communication, E. M. Kindle. 



