68 NEV/ YORK STATE MUSEUM 



York (D. h a m a t u s Conrad) and from the equivalent horizon Etage G, 

 of Bohemia (D. monstrosus Barrande sp.). The species from Cape 

 Barre (D. 1 i m e n a r c h a) is represented only by an incomplete cephalon 

 but it is rarely that any other part of the genus has been observed in any 

 of its occurrences. It was a species larger than the New York form and 

 perhaps even larger than the Bohemian. Its elongate, subconate middle 

 lobe is well delimited by a deep nuchal furrow, the lateral lobes are sepa- 

 rated by a shallow transverse or oblique groove, while the axial diameter of 

 the occipital ring from the base of the central lobe to the fork of the spine 

 is relatively less than in D. ham atu s. The free cheeks were attached to 

 this specimen, but they have not been preserved except along the sutures. 



The great neck spines are highly diver- 

 gent and very heavy. Barrande gave the 

 angle of divergence in D. monstrosus 

 as 60°, in D. h a m a t u s it is 45°, in 

 D. limenarcha it is 80", measured 

 from the central occipital tubercle as apex, 

 axially for one third of the length of the 

 spines. These spines are curved outward, 

 downward and back, and probably made 

 a deep recurvature as in the other species, 

 though they are not preserved at the tips. 

 On their proximal extent is a low median 

 depression. The surface of the head is 

 covered with acute pustules scattered 

 Dicranuius limenarcha sparsely wltli Very uiuch finer ones 



between. On the occipital ring the cen- 

 tral pustule, which is more conspicuous than the rest, as in other species, is 

 punctuated at the top by a circle of depressions. The head had an original 

 length to the point of recurvature of the neck spines of about 40 mm, the 

 greatest divergence of the spines is 29 mm, the axial length to the angle of 

 the spines, 23 mm, of Avhich 9 mm belong to the occipital ring ; width 

 between the eyes, 25 mm. 



From no other evidence have we so satisfactory a basis for the con- 

 clusion that the Cape Barre beds follow close below the beds of Perce rock 

 and above those of Mt Joli. We may therefore conclude that either these 

 strata lie buried in the tide-swept interval between the Perce rock and the 

 outermost vertical strata belonging to the Mt Joli massive, or that, originally 

 in place here, they have been pushed out by faulting. The space betM^een 

 these two massives not in the line of the connecting sand spit but rather 



