F. R. Cou'per Reed — Blind Trilohites. 497 



so that the head-shield has retained its early larval features. I do 

 not, however, see that the evidence in favour of putting C. mutilus 

 with the Proetidge, or any other such high group, is stronger than 

 that of putting it in the Conocoryphidte. It is to be noticed, 

 moreover, that the genus Proetus has not been recorded from Etage 

 D, except the doubtful species Pr. ? primulus (Barr.) from Dd 1 

 and Pr. ? perditus (Barr.) from Dd 5. 



There is considerable uncertainty about the true position of the 

 genus Eolocephalina (Salter).^ It is placed by Zittel in his 

 somewhat heterogeneous family Conocephalid£e, together with 

 Arionellus, to which, as Salter remarks (loc. cit.), it shows 

 some points of resemblance. There see'ms to me little reason for 

 associating it with the Asaphidee, as Beecher does in his scheme 

 of classification. It is very doubtful if eyes are present in either 

 of the two known species, though Salter records them on the 

 minute free cheeks of H. primordialis, at the base of the genal 

 spines. The free cheeks in this species consist almost entirely of 

 the genal spines and do not extend along the cephalic margin, and 

 in this way remind tis of those forms (e.g. Triniicleus) in which the 

 eyes are absent.^ In JP. inflata no genal spines or free cheeks 

 are known, and it appears to me that this genus is in reality 

 a Conocorj'phid with incipient free cheeks, as in the metaprotaspis 

 stage of Ptychoparia Kingi,^ and that the loss of segmentation in the 

 glabella and other signs of specialization are secondary features, 

 as in Agnostus. The fact that HolocepJialina is confined to such 

 an early stratigraphical horizon as the Menevian is also against 

 regarding it as a degraded or degenerate higher form. Arionellus 

 is an allied genus, but it has well developed, though narrow, free 

 cheeks, bearing distinct eyes, which are a mark of a higher stage in 

 the evolution of the cephalon. 



Passing now to the family Olenidse, which is fbr the sake of 

 convenience split up by Beecher into four subfamilies, we meet 

 first with a group of genera which are generally considered to 

 possess eyes on the free cheeks, though varying much in size and 

 degree of development. But with regard to the genus Paradoxides 

 in the subfamily Paradoxinee, there has long been much dispute 

 as to whether it was possessed of the power of vision or not. 

 By some paleeontologists the eye-socket is held to have been 

 occupied by no functional visual organ, but generally this 

 genus is described as furnished with long narrow eyes. Beecher 

 (loc. cit.) does not make any mention of its supposed blindness, 

 nor does Zittel. Salter, Hicks, and other British writers who 

 have described its species always speak of the presence of eyes 

 without suggesting their non-functional nature ; but the visual 

 surface and lenses have never been described, and the surface of 



1 Q.J.G.S., vol. XX (1864), p. 337, pi. xiii, fig. 9 ; toI. xxviii (1872), p. 178, 

 pi. -vi, figs. 8-10. 



^ Barrande (Syst. Sil. Boh., Suppl., toI. i, p. 156) remarks tliat, judging from 

 the figures, this species seems to be devoid of eyes. 



2 Amer. Geol., vol. xvi (1895), pi. viii, fig. 6. 



DECADE IT. VOL. V. — NO. XI. 32 



