494 F. R. Coioper Reed — Blind Trilohites. 



The development of several genera of the order Opisthoparia has 

 been traced in detail, and in the family Conocoryphidse, which is 

 placed by Beecher lowest in the order, we find the characters of 

 a pre-adult stage of certain Oleuidte preserved till maturity. la 

 fact, the adult Conocoryphe is in the nepionic stage of such genera 

 as Ptychoparia and Sao, and this fact shows that it belongs to 

 a lower phylogenetic rank. The free cheeks are very narrow and 

 marginal, and the eyes are absent or very rudimentary. Owing, 

 unfortunately, to the loose manner in which the name Gonocoryplie 

 has been ajDplied, and the confusion arising from its different 

 usage by palseontologists, it has frequently been stated that the 

 genus includes a majority of species possessing compound eyes 

 and a few which are blind ; and, consequently, it has been 

 quoted as analogous to those genera of which the species living 

 in twilight or darkness have almost or completely lost their 

 eyes. Conclusions based on this mistaken analogy are naturally 

 erroneous and misleading. A structural feature which is really of 

 high phylogenetic significance has been misinterpreted as an adaptive 

 modification induced by certain conditions of existence. 



The name Conocoryphe should be applied in the manner in which 

 its author, Corda,^ first used it, when he took as its type the well-known 

 blind form Conocoryphe Suheri. Matthew has insisted on this point, 

 and when the genus is thus restricted so as only to include forms 

 agreeing with this type in important structural characters, a large 

 number of species which are commonly ascribed to this genus 

 have to be excluded. Thus, of the numerous British species which 

 have been described as belonging to the genus Conocoryphe, only 

 C. bufo (Hicks) and perhaps C. hiimerosa (Salter) can be admitted.^ 

 Barrande* included in his genus Conocephalites a large number of 

 species possessing eyes, as well as C. Suheri and others devoid of eyes, 

 so that Conocephalites practically covered Corda's genera Ptychoparia, 

 Ctenocephalus, and Conocoryphe. 



Walcott* says that the genus Conocoryphe, in its restricted sense, 

 is identical with Emmons' genus Atops, and Vogdes^ takes Corda's 

 Conocoryphe Suheri (Schlotheim^) as the type of the genus Atops. 

 Beecher,' however, takes this species as the type of the genus 



1 Hawle and Corda, Prodr. Mon. Boh. TrUob., 1847, p. 24, t. ii, f. 10. 



^ C. Sotnfrayi (Salter) is stated to possess eyes, but from a careful examination of 

 tbe type -specimen, which is much compressed and distorted, I have much doubt 

 if they truly exist. In C. Zyelli (Hicks) the free cheeks are marginal, and the eyes 

 ■which have been described appear to me to be merely the swollen ends of the ocular 

 ridges on the fixed cheeks, and their visual function is doubtful. In cephalic 

 structure this species agrees so closely with the Conocoryphe, s.str., of Corda, that 

 after carefully examining the type-specimen, I am inclined to consider it a true 

 member of the genus Conocoryphe and to be devoid of compound eyes. 



^ Barrande, Syst. Sil. Boh., vol. i, p. 416. 



* Bull. 30 U.S. Geol. Surv., 1886, p. 203 ; Amer. Journ. Sci., ser. iii, vol. xxxiv 

 (1887), p. 197; Fauna of the OleneUus Zone, 1890, p. 647; S. W. Ford, Amer. 

 Journ. Sci., ser. in, vol. xix, p. 152. 



s Bibliogr. Pal. Crust. (California, 1893), p. 255. 



^ Schlotheim, JSTachtrage z. Petrefakt., ii (Gotha, 1823), pi. xx, fig. 1, 



■^ Amer. Journ. Sci., vol. iii (1897), p. 188. 



