PALEONTOLOGIC CONTRIBUTIONS I3I 



is shown (se pi. 36, figs. 3, 6, 8) that probably contained a 

 lens in Asaphus laevissimus, 1 As. judibundus 

 (ibid. pi. 8, fig. 16); Basilic us kegelensis, 2 N ileus 

 armadillo (ibid. pi. 8, fig. 13), Megalaspis acuti- 

 cauda var. t y p i c a. a In a few of Schmidt's photographs two 

 pits are observable, suggesting the presence of two lenses. This is 

 the case in Asaphus eichwaldi {op. cit., Lief. II, p. 41, 

 fig. 28a). 



Having noted the peculiar tubercle on the top of the bulgy gla- 

 bella of Cryptolithus (Trinucleus) we searched our specimens for 

 evidence of lenses in these. It was found that the numerous shale 

 specimens from the Lorraine beds, which have lost their lime 

 content, exhibit only the exterior surface but afford the significant 

 observation that while in Cryptolithus (Trinucleus) 

 tesselatus the surface of the cheeks and glabella is finely 

 pitted, the top of the tubercle is smooth, exactly as in the eye spots 

 on the cheeks. In the specimens from the Trenton limestone the 

 glabella is usually exfoliated, the test adhering to the matrix. 

 These for the most part give a cast of the interior of the eye 

 tubercle with a well-preserved and regular apical pit. This pit was 

 also found to be finely preserved in a specimen of C. (T .) 

 b u c k 1 a n d i ( see pi. 34, fig. 5) from the Ordivician of Girvan, 

 Scotland. In this specimen the top of the tubercle is black in 

 contrast to the light buff -colored rock, suggesting that the pigment 

 of the ocellus may be preserved. 



In a considerable number of the Trenton limestone specimens, 

 however, the upper portion of the tubercle is glossy, dark and 

 smooth, and therefore so distinctly set off from the surrounding 

 surface which is densely pitted that it appears like a black pearl 

 set in a little mound and can not help suggesting at once the 

 presence of a separate lens (see pi. 34, figs. 2 and 3; pi. 35, 

 figs. 1 and 2). This body is rather strongly conical upward, 

 fairly well defined in outline toward the pitted surface, and when 

 broken out, considerably flatter on the under side. In thin sections 

 (see pi. 35, fig. 2), the lens, in spite of its crystalline aspect, 

 due to its smooth surface, appears to be composed of the same 

 fine-grained brownish lime-mud as the matrix of the rock, but also 

 set off by a distinct carbonaceous line on the under side. It is 



1 See op. cit., Lieferung 1, pi. 5, fig. 4. 



2 See op. cit., Lief. II, pi. 5, figs. 1 and 4. 



3 See op. cit., Lief. V, p. 43, fig. 19. 



