1918] 



The Ottawa Naturalist 



33 



Two independent and slight departures from the 

 unmodified Dalmanitina line showing obsolesence of 

 the anterior furrows are here provisionally retained 

 within it. They embrace in the Ordovician forms 

 like D. phillipsi Barrande and in the Silurian the 

 species D. logani Hall. 



Other slight departures from the primitive stock, 

 exhibiting a considerable broadening anteriorly of 

 the glabella, are retained under Dalmanitina. They 

 include Phacops (Acasie) alifrons Salter and P. 

 jamesii Portlock, both from the Ordovician. The 

 Ordovician Phacops brongniarti Portlock is prob- 

 ably a more considerable modification of the normal 

 Dalmanitina, but without actual study of specimens 

 of this species, it would not be wise to determine 

 its affinities in any detail. It is apparently the 

 nearest approach to the Phacopinae in the Ordovician 

 in one character at least, reference to which has been 

 made on a previous page. 



In a more extended revision of the Phacopidae it 

 may be found wise to erect subgenera for these 

 slightly modified Da/mani/ina-like forms. A new 

 subfamily might also be erected to include Phacopina 

 Clarke, Dalmanitina Reed and the new subgenera. 

 Such a subfamily would then embrace the entire 

 primitive or little modified stock of the Phacopidae. 



Genotype: Dalmania socialis Barrande. 



Dalmanitina logani var. conservatrix, n. var. 

 ( conservatrix, preserver). 



This variety only differs from Dalmanitina logani 

 (Hall) by having all the glabella furrows well im- 

 pressed but all gradations exist between them. Com- 

 pared with Dalmanitina doivningiae (Murchison) 

 the frontal lobe is a little higher, the third side lobes 

 slightly smaller, and the glabella surface variably 

 tuberculose. The pygidium is mucronate and with a 

 proportionately more slender and tapering axis. The 

 cephalon is a little more than twice as wide as high. 

 The maximum width is about 22 m.m. The average 

 pygidium is 13 m.m. wide and 8 m.m. long. 



Horizon and Locality. Rare in the Moydart and 

 Stonehouse formations, Arisaig, N.S. 



Collections. Victoria Memorial Museum, Yale 

 University collections. 



Genus Phacopina Clarke. 



1890. Phacops Clarke, Archiv. do Mus. Nac. do 

 Rio de Janeiro, 9, pp. 15-16, est. 1, figs. 1-3. 



1905. Phacopidella Reed (partim), Geol. Mag., 

 (5), 2, p. 226, footnote 1. 



1913. Phacopina Clarke, Mon. Serv. Geol. E. 

 Min. do Brasil, vol. 1 , p. 151. 



Dalmanitinids in which all but the third pair of 

 lateral glabella lobes are fused together. They lack 



the broad expanding glabella with greatly reduced 

 third pair of side lobes of the Phacopinae. They 

 also differ from the coeval Phacoplnids by having 

 a much more depressed and non-tuberculose glabella. 

 It probably represents an early Devonian or late 

 Silurian modification of the Dalmanitina stock. The 

 genus is, therefore, placed in the subfamily Dal- 

 manitinae. 



Genotype: Phacops braziliensis Clarke. 



Genus Dalmanites Barrande. 



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

 Centre Boheme, I , p. 934. 



1904. Dalmanites Reed, Geol. Mag., (5). 2, 

 p. 224. 



1913. Dalmanites Raymond, Zittel - Eastman 

 Textb. Pal., p. 726. 

 Genotype: Trilohus caudatus Brunnich. 



Subfamily Phacopinae Reed. 

 Genus Phacopidella Reed s. str. 



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

 Centre Boheme, 1, pp. 525-528. 



1905. Phacopidella Reed (partim), Geol. Mag., 

 (5), 2, p. 173. 



1911. ClocJferia Wedekind, Zeitschr. Deutsch. 

 Geol. Ges., vol. 63, p. 323. 



Phacopidella Reed was erected in 1905 as a 

 subgenus of Phacops Emmrich and was given a very 

 broad interpretation. As already noted it was made 

 to include the generalized Silurian forms which 

 above have been placed under Dalmanitina Reed. 

 Its author also included in it the Silurian group of 

 P. stof(esii, for he restricts Phacops Emmrich to the 

 Devonian assigning all intermediate Silurian forms 

 to Phacopidella and in 1 906 refers Trilobites elegans 

 Sars and Boeck to subgenus (of Phacops J Phacopi- 

 della. In addition he placed it in the Devonian 

 group of P. braziliensis Clarke, which above has 

 been shown not to be Phaccpinid and for which 

 Clarke created his genus Phacopina Clarke. The 

 last and fourth group was that of P. glockeri 

 Barrande. Since the genotype chosen by Reed 

 (net P. donmingiae as supposed by J. M. 

 Clarke, 1913, p. 150) lies within this group, 

 Phacopidella is now restricted to it. This confines 

 it in time to the later Silurian and geographically to 

 the Tethys (Bohemia) realm. In 1911 Wedekind 

 proposed the generic name Clockeria for this group. 

 Phacopidella having priority, Wedekind's name of 

 course cannot stand. 



Phacops glockeri Barrande, P. trapeziceps Bar- 

 rande, and P. bulliceps Barrande are referred to the 

 genus as restricted. The glabella of the last named 

 species is not so broad and is more rounded anter- 



