268 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



Olenellus Bernard, 1894, Quart. Journ. Geol. Soc. London, Vol. 50, pp. 

 415-416. (Discusses evidence afforded by this genus as to the sys- 

 tematic position of the trilobites.) 



Mesonacis (Olenellus) Peach (in part), 1894, Idem, pp. 671-674. (As 

 discussed in these pages this genus includes forms now referred to 

 both ElUptocephala and Mesonacis.) 



Elliptocephala (Emmons), Beecher, 1897, American Journ. Sci., 4th ser., 

 Vol. 3, pp. 191 and 192. (Name used in discussion of genera of the 

 Olenidae.) 



Georgiellus Moberg, 1899, Geol. Foren. i Stockholm Forhandl., Bd. 21, 

 Hafte 4, p. 317. (Proposed as a new genus to replace Elliptocephala.) 



Elliptocephala (Emmons), Matthew, 1899, American Geologist, Vol. 24, 

 p. 59. (In review of Moberg's paper [1899] considers that Ellipto- 

 cephala should be retained.) 



Olenellus {Georgiellus) Pompeckj, 1901, Zeitschr. Deutschen geol. Ge- 

 sellsch.. Vol. SZy Heft 2, p. 16. (Emmons' species is merely mentioned 

 as " O. {Georgiellus) asaphoides" in the discussion of the relations 

 between Olenopsis and various genera of the Mesonacidse.) 



Olenellus Linpstrom, 1901, Kongl. Svenska Vet.-Akad. Handlingar, Vol. 

 34, No. 8, pp. 12-18, and 24. (A discussion of the development of the 

 Olenellidae is almost entirely based upon features exhibited by the 

 type species of the genus Elliptocephala.) 



The characters of the genus are outHiied in the description of the 

 genotype, E. asaphoides, which is the only known species. Observa- 

 tions on Elliptocephala are also made in the section on Mesonacidse 

 (pp. 244 and 247). 



Genotype. — Elliptocephala asaplwides Emmons. 



Stratigraphic range. — Lower Cambrian : Greenwich formation ^ in 

 shales and interbedded Hmestones and sandstones of unknown thick- 

 ness, but as far as known not over 300 feet. 



Geographic distribution. — On the eastern side of the Hudson River 

 valley, in Washington and Rensselaer counties, New York. 



Young stages. — Reference is made to the younger stages of growth 

 of this genus in the description of the development of the individual 

 of the family Mesonacid?e. p. 236. This, with the illustrations on 

 plates 24 and 25, will give the student the means of comparison 

 with the young stages of other genera. The specimens in the Ford 

 collection are now in the New York State Museum at Albany. New 

 York. 



^ Mr. T. Nelson Dale [1904, p. 29I gives a section of the Lower Cambrian 

 series exposed in Rensselaer County, and part of Columbia County, New York. 

 On pages 43 and 50 he states that this series is regarded as equivalent to the 

 Greenwich formation of Washington County, New York, and Rutland County, 

 Vermont. The series is also regarded as equivalent to the Vermont formation 

 and is mapped on plate i of the same paper under the heading " Greenwich slate. 



