40 BRITISH CAMBRIAN TRILOBTTEK. 



Family Shumardiip2E. 



The genus Shumardia has by some writers been placed in the family 

 Agnostidae. Moberg, 1 however, in 1890 pointed out that it presents scarcely any 

 resemblance to Agnostus, except in the absence of eyes and facial sutures, and ho 

 concluded that it belongs rather to the Olenidae. At a later date Pompeckj - 

 considered it to be most closely related to Ccmoconjphe ; while Reed, 3 like Moberg, 

 included it in the Olenidre. In the absence of eyes and the marginal position of 

 the facial suture it resembles the Conocoryphidae ; but it differs in the form of the 

 glabella, the small number of thoracic segments, the structure of the pleura 1 , and 

 the comparatively large size of the tail. Its stratigraphical position, also, would 

 be remarkable for a member of that family. 



Some authorities have supposed that it may be the young of one or other of 

 the genera which are found associated with it ; but the large number of specimens 

 which have now been found, in widely separated localities, and the entire absence 

 of forms intermediate between it and any other recognised genus, render this view 

 highly improbable. If it be a larva the change to the adult form must have been 

 as abrupt and almost as striking as the change from the chrysalis to the butterfly ; 

 and of such violent metamorphosis we have no evidence in trilobites. 



It is an aberrant genus, the affinities of which are not yet determined ; and for 

 the present it is most convenient to place it in a family of its own. 



Genus SHUMARDIA, Billings. 

 1. Shumardia pusilla (Sars). Plate III, figs. 18—20; Plate IV, figs. 1 — 1. 



1835. Battus pusillus, Sars, Okens Isis, 1835, col. 334, pi. viii, fig. 2 a, b. 



1838. Trilobites pusillus, Boeck, Keilliau's Ga?a Norv., p. 144. 



1865. Agnostus (Olenus ?) pusillus, Kjerulf, Veiviser ved geol. excursioner i Christiania omegn, p. 2, 



and p. 3, fig. 10. 



1874. Conophrys salopiensis, Callaway, Quart. Journ. Geol. Soc, vol. xxx, p. 196. 



1877. Conophrys salopiensis, Callaway, loc. cit., vol. xxxiii, p. GG7, pi. xxiv, fig. 7. 



1882. Conophrys pusilla, Brogger, Die Silur. Etagen 2 und 3, p. 125, pi. xii, fig. 9. 



1890. Shumardia pusilla, Moberg, Om en afdelning inom Olands Dictyonemaskiffer, p. 4, figs, a — c. 

 1902. ? Shumardia miqueli, Pompeckj, Neues Jalirb., 1902, vol. i, p. 5, fig. 2 a, b. 



1902. Shumardia bottnica, Wiman, Bull. Geol. Inst. Upsala, vol. vi, p. 65, pi. iii, figs. 35 — 38. 



1902. Acanthopleurella grindrodi, Groom, Geol. Mag., new series, decade iv, vol. ix, p. 70, with 



4 figs, (a young form). 



1906. Shumardia pusilla, Moberg and Segerberg, Ceratopygeregionen, p. 80, pi. iv, figs. 10 — 12. 



1906. Shumardia bottnica, Moberg and Segerberg, ibid., p. 81, pi. iv, figs. 13 — 16. 



1 Om en afdelning inom Olands Dictyonemaskiffer, p. 7. 



2 Neues Jahrb., 1902, vol. i, p. 7. 



3 Trilobites of the Girvan District, Palseont. Soc, 1903, p. 42. 



