PALEONTOL0G1C CONTRIBUTIONS IO3 



the American species. Other species have been described from 

 Sweden. Lately Assar Hadding 1 has figured a continuous series of 

 eight valves of A . ? elongatu's Hadding from the graptolite 

 zone with Amplexograptus vasae Tullb. We have a 

 continuous series of four plates (see pi. 32, fig. 7). 



The plates of A . w a r d e 1 1 i are somewhat variable in shape ; 

 in general they have the outline of an oblique parallelogram with 

 one short side truncated (pi. 32, figs. 1, 2, 5, 8) ; others are simply 

 rhomboidal (pi. t,2, fig. 9). In the long quadrangular plates the 

 truncated short side is drawn out into a projecting point or apex 

 (see pi. 32, figs. 3, 6, 8). The opposite short side is very oblique and 

 truncate at the dorsal margin (see pi. 32, figs. 2 and 5). The longer 

 plates are quite convex, the largest are fairly semicircular in section 

 and the four sides are in some more or less well rounded, especially 

 also the truncated side. The smaller rhomboidal ones are either 

 nearly flat with a keel on one side (pi. 32, fig. 8) or rooflike (pi. 32, 

 fig. 9). The larger plates have at the truncated end two diverging 

 grooves or sutures (see pi. 32, fig. 2) which in the mold of the 

 interior (pi. 32, fig. 5) appear as ridges and were therefore double 

 grooves on the inside and outside. One of the long sides (dorsal ?) 

 was bent rectangularly and possessed a flange. The surface was 

 uniformly ornamented with fine, mostly parallel, but also anas- 

 tomosing striae (5 in 1 mm) which start from the apex (see pi. 

 ^2, fig. 3) and become parallel to the long sides of the plates. 



A fragment of the organism, consisting of four plates, was 

 obtained (see pi. 1,2, fig. 7). This consists of the rhomboidal 

 plates which are hardly overlapping. The rhomboidal plates 

 measure 7 by 7 mm or less, the largest ones of the others reach 

 26 by 13+ mm in size. 



The interior surface of the plates is worthy of special notice. It 

 is covered with an extremely delicate network of chitinous fibers 

 which form polygonal meshes, the points of intersection being 

 thickened. Whether this meshwork was imbedded in a calcareous 

 matrix or exposed free on the inner surface is difficult to decide. 



From the great differences in outline, shape and section of the 

 plates we infer that probably the larger and more rounded 

 plates, belonged to the capitulum, while the smaller, rhomboidal 

 ones may have formed the pedicle. The latter were but slightly if 

 at all overlapping, but it can be inferred' from the form of the 



1 Assar Hadding. Der mittlere Dicellograptus-Schief er auf Bornholm. 

 Meddelande fran Lunds Geollogiska Faltklu'bb, ser. B, no. 8, p. 31. 1913. 



