38 LINDSTRÖM, VISUAL ORGANS OF THE TRILOBITES. 



A. acuminatus Nieczkowski, Zusätze zur Monogr. der Trilobiten 1859», tab. I, f. 6. 

 Maculie most prominent, but no mention made of them in the description 



A. (Isotelus) canalis J. Hall, Pal. N. Y. I, pl. 4 bis, f. 18—19. Though this and 

 a following species probably on account of the deviating conformation of their body, 

 belong to a different genus or subgenus, I mention them along with the Asaphi, as 

 there is the greatest similarity in their hypostoma. Fragment of an interiör cast; still 

 raore stränge is the fragment showing part of the interiör surface and the duplicature. 



A. expansus L. Bit. 1 pl. VII f. 3, Br. II pl. I f. 2, 2 c. In the two tirst figures 

 there are no tubercles nor maculae marked, in the last figure there are distinct tubercles. 



A. fallax A. pl. XXVIII f. 3, e. Br. II pl. I, f. 3, both nearly congruent. 



A. {Isotelus) gigas J. Hall, Pal. N. Y. I, pl. 60, f. 7 g, pl. <66 f. 5, the inside of 

 au entire, uncommonly large hypostoma gives a general good view with the maculae which 

 are large and evident. He mentions the maculae as »two circular spöts . These probably 

 indicate the points for the attachment of muscles and tendons upon the inside,» he adels. 



A. ingen* Bahr. Novak II, pl. I, f. 7, "a good figure showing two semiglobular ma- 

 culie. Barrande's figures pl. 33, f. 7, 8 are not distinct, 



A. ludibundus Tqt. Bil II, pl. 1, f. 7. Two semilunar sulci on the cast of the 

 interiör surface, being only the posterior borders of the maculaa which are a little more 

 raised and distinct than the rest. 



A. nobilis Barr. pl. 32, f. 6. Indistinct traces of macula?. In the figure (i, pl. 31 

 representing the hypostoma of a young specimen, there are no tubercles at all. Ii' the 

 figures were to be relied upon, it inight he assumed, that the tubercles appear at a more 

 raature age. 



A. Powisii Salter, pl. 23, f. 6. Two semilunar, narrow tubercular macuhe, their 

 interiör apices converging towards the anterior horder of the hypostoma. 



A. raniceps A., pl. XXVIII, f. 2c, Br. II, pl. 1, f. 4. A good figure. 



A. raniceps var. maxima Br. Il, pl. 1, f. ti. Semilunar impressions on a cast and 

 thus far incomplete. 



A. striatus Boeck. To this belongs probably A. expansus M. Saks »Ueber einige 

 neue öder unvollständig bekannte Trilobiten» in Isis 1835 p. 333, and especially p. 340 

 and the following (Bemerkungen iiber die untere Seite von einigen Trilobiten). Saks 

 there gives a verv good description of the exteriör side, where he also mentions the two 

 maculae, pl. IX, f. 9 a, b. (»2 kleine Knoten»), Br. I, pl. VIII, f. 4 a, and Bil II, pl. I, f. 9. 

 These latter figures differ in so far, that the former has the maculae excavated or rather 

 tubular below, in the latter again they are regular. 



A. trinucleorum Br. II, pl. 1, f. 16 a large specimen with linear maculae arranged 

 rectangularly in respect t<> the longitudinal axis of the hypostoma and both on the 

 same level. 



A. tyrannus Murch. Saltek in Mem. Geol. Survev, Brit. Foss. Dec. II, 1849 pl. V, 

 f. 4, excellent figure. On p. 2 he says: »there i-- an oval circumscribed tuberele at the 

 origin of each (1'ork) most distinct on the inner surface». This figure is again repro- 

 duced in the »Monograph», pl. 22, f. ti, where it is said »Two linear tubercles with their 

 interiör apices converging towards the posterior margin of the hypostoma». 



