F. R. Coioper ReedT-On the Cheiruridce. 207 



The last-mentioned genus was only provisionally united witli the 

 others. Salter/ while omitting Flacoparia from the above list, 

 added Amphion, which Barrande placed in the family containing 

 Encrinurus, etc. The genus or subgenus Splicerocoryphe was also 

 really included by Salter, but under the name of Stanrocephalns ? 

 unicus. The genera Encrinurus, Cybele, and Zetlius were also given 

 by Salter as belonging to the Cheiruridse, but with a query 

 against each of them. Zittel" places the following genera in 

 this family : Cheirurus (with its subgenera, Cheirurus, s.s., Cyrto- 

 metopus, Sphcerocoryphe, Crotalocephalus, EccoptocheUe, P seudo splicer- 

 exochus, and Nieszhowslcia), Areia, Deiphoiy, Onychopyge, Placoparia, 

 Splim'exochns, ? Crotalurus, Staurocephalus, Amphion, Diaphanometopus. 

 Of these, Crotalurus must certainly be at once removed to another 

 family and group, because of the course of its facial suture.^ 

 More recently, Beecher,^ in a valuable and suggestive paper 

 on the classification of trilobites, has enumei'ated the genera and 

 subgenera in this family thus : Cheirurus, Actinopeltis, Amphion, 

 Anacheirurus, Ceraurus, Crotalocephalus, Cyrtometopus, Deiphon, 

 Diaphariometo'pus, Eccoptocheile, Hemisphtxrocoryphe, Nieszkowslda, 

 Onychopyge, P seudosphcerexochiis, Sphcerexochus, SpiJuerocoryphe, Stauro- 

 cephalus, Youngia, Eliminating the subgenera we get the following: 

 Cheirurus, Amphion, Deiphon, Diaphanometopus, Onychopyge, Sphcer- 

 exochus, Sphmrocoryphe, Staurocephalus, and Youngia. Sphmrocoryphe 

 must, in my opinion, be accorded generic rank. The genera Placoparia 

 and Areia are placed by Beecher in the Encrinuridse on account of 

 their larval features, which suggest their union with this more 

 primitive and less specialized family. In fact, he would apparently 

 regard these two genera as morphologically the lowest in the 

 phylogenetic list of the members of his order Proparia, which com- 

 prises the four families Encrinuridee, Calymenidas, Cheiruridae, and 

 Phacopidge. 



Omitting the imperfectly known and extra - European genus 

 Onychopyge, we may concentrate our attention on the other genera 

 which have been accorded a place in the Cheiruridse, and all of which 

 are found in Europe. The four genera Placoparia, Areia, Amphion, 

 and Diaphanometopus are those whose true position is most a matter 

 of doubt. Schmidt,^ for instance, hesitates somewhat in retaining 

 the two last genera in the CheiruridEe ; and the different views of 

 Salter, Barrande, Zittel, and Beecher with regard to Amphion and 

 the others have been mentioned above. The question can only 

 be decided by the characters which one considers as essential 

 to the family. But it is a matter of minor importance how we 

 group together the genera in a system of classification, so long as 

 we understand their phylogenetic relations. In Areia, in the first 



1 Salter, Mon. Brit. Trilob. Palseont. Soc. (1864), p. 2. 



^ HandWh der Palaontologie (1885), vol. ii, p. 616. 



' Ie Zittel's " Grundziige der Palaontologie " (1895), this genus is omitted from 

 the Cheiniridfe. 



* Amer. Joiirn. Sci., vol. iii (1897), p. 89. 



3 Mem. Acad. Imp. Sci. St. Petersb., vol. xxx, No. 1 (1881) : Eev. ostbalt. 

 TrH., Abth. i, pp. 190, 195. 



