Dr.F. R. Coioper Reed — The genus Homalonotus. 319 



of two families, the Calymenidse and the Homalonotidse, and Giirich ' 

 in 1908 adopted this classification. Swiimerton^ in 1915 followed 

 Giirich, but put the two families in a section Calymmenuia of a sub- 

 order Conocoryphida, which he ascribed to Beecher's group Opisiho- 

 paria because of their supposed derivation from tlie Oleiiidse. 



The family Calymenidas (in its wide sense, including Homalonotus) 

 Avas put by Beecher in 1900 and by llaymond in 1913 in the group 

 Proparia on account of the course of the facial sutnres. But Giirich 

 (op. cit.), finding a difficulty in placing it in either of these groups, 

 instituted a new group, whicli he called Gonatoparia, for those genera 

 in which the facial sutures cut the genal angles, and he placed the 

 Calymenidas and Homalonotidse in it. Koch, however, had seen that 

 some of the Devonian species had the point of section in front of the 

 genal angles, and it is not improbable that some of those from the 

 Gres de May possessed the same character. If, therefore, we are of 

 opinion that Beecher's scheme and principles of classification of 

 the Trilobita are natural and generally applicable, it seems as if 

 Homalonotus sliould be associated with the Proparia rather than 

 with the Opisthoparia. The idea of the derivation of Homalonotus 

 from the Olenidse, and therefore of its place in the Opisthopariay 

 lias arisen from its supposed relation to Hicks' unfortunate genus 

 JSfeseuretus, which Pompecki referred to the Olenidae, having failed 

 to see that it was of a composite character. So much confusion and 

 misunderstanding appears to have arisen ixhout the ^&ti\\& Neseuretus 

 that a few remarks upon it may here be made. The type-specimens 

 (all of which are poor) are mostly in the Sedgwick Museum and have 

 been studied by myself. The first-described species, N. ramseyensis, 

 Hicks, ^ is apparently identical with Calymene Trista7ii, Brongn., 

 which was chosen by Pompecki as the type of his genus SynJiomalo- 

 notus. The second described species, N. quadratus, Hicks,* is an 

 indisputable Homalonotus belonging to Salter's group Brongniartia. 

 The third species, N. recurvatus,^ is probably referable to Calymene 

 and seems to resemble H. Heherti, Barrois,* from the Gres armoricain. 

 The fourth species, N.'i elongatus, Hicks,' may also belong to 

 Calymene, but the type is in a poor state of preservation, so that 

 the characters are difficult to distinguish. It is now ascertained 

 that the beds from which these specimens came are of Arenig and 

 not Tremadoc age. From the above remarks it appears that 

 Ne&euretus must be regarded as a composite and heterogeneous 

 assemblage of species and it has no right to be retained as a separate 

 generic designation. 



Apart from all other distinctions the fundamental difference 

 between Homalonotus and Calymene seems to be that in tiie former 



^ Giirich, Leitfossilien, Lief, i, Camb. Silur., 1908, p. 70. 

 2 Swinnerton, Geol. Mag., Dec. VI, Vol. II, pp. 494, 540-3, 1915. 

 ^ Hicks, op. cit., p. 44, pi. iii, figs. 7-10, 16-22. 

 * Ibid., p. 45, pi. iii, figs. 11-13, 23-6. 

 ^ Ibid., p. 45, pi. iii, figs. 5, 6. 



" Barrois, Bull. Soc. Geol. France, ser.iii, vol. xiv, p. 802, pi. xxxvi, fig. 14, 

 1886. 



' Hicks, op. cit., p. 45, pi. iii, figs. 1-3. 



