RONGL. SV. VKT. AKADEMIENS ÖANDLlNGAR. HAND 34. n:o 8. 53 



D. Mac Coyi Barr. Supl., pl. 13 I. 32. Tliis magnificenl hypostoma belongs to 

 t lic same grourJ ;is 1). micrurus Hall as to which we may hesitate whether there no1 be 

 a double pair of maculse above each other near the posterior börder. In this species, 

 however, there is the transverse lower groove and above probably the two macula? united 

 by a groove so closely as to resemble the lower groove. 



D. micrurus J. Hall, PaL N. V. III pl. 71 fig, 20. Shows, as it were, a double 

 pair of maculae, very like D. spinifer Barr. 



D. rugosus Barr. pl. 24 f. 23. The two maculae in the ordinary place, without 

 being united by a groove. 



D. social is Barr. pl. 2G f. 21. Rather of an nneonnnon ghape, nol so trianguläras 

 in the other species, the two maculae distinct as narrow slits. P. 553 »Vers l'extrémité 

 du corps central, on apercoit de chaque CÖté, prcs du hord, nne impression oblique, aloii- 

 gée et arquée». 



D. spinifer Barr. Pl. 25, tig. 20. A large beautifully preserved hypostoma, shows 

 what 1 think we positively must interpret as a double pair of maculae close above each 

 other. As stated above there is reason to believe that in other species of Dalmanites 

 there also are indications of four macula 1 , though not so evident as in tliU species. 

 Barrande says nothing about this remarkable feature. 



Dalmanites imbricatulus Angelin. 



Pl. III figs. 43, 44. 



The interesting image, as o-iven by the agglomerated cyes, is represented in the 

 magnified figure 43 Plate III. The lenses lic there separated from each other at much 

 varying distance, some in close contact. The presencc of the delicate covering membrane 

 is clearly scen, being of white colour contrasting with the black, glossy lens. It is much 

 lacerated and only preserved around the periphery. The size of the ocelli is on an 

 average 0,.-. mm., a little one has 0,3 mm. The surface between the ocelli is most finely 

 granulated. The granules scarcely attaining the fourth of the granules in Dalm. vulgaris. 



In a vertical section the regular biconvex len ses are seen to be covered with the 

 extremely thin integument, which is a direct continuation from the test. The test be- 

 tween the lenses is perforated by some longitudinal tubes, as nsnal in the skeleton of 

 the trilobites. We have not found any hypostoma with the maculae. 



Dalmanites obtusus LnM. 



Pl. III figs. 45, 46. 



We have not succeeded in iinding any hypostoma, but as the strueture of the 

 cephalic eyes is sufficiently well preserved, we here describe it. The lenses seen from 

 the surface look globular, and in a vertical section they are ovate and in a horizontal 

 circular. They are covered by a very thin and delicate membrane, that envelops their 

 superior moiety completely and between the eyes it is enclosed by the surrounding test 

 and growing out from it. In the horizontal section, tig. 45, it looks as a circular frame 



K. Sv. Vet. Akad. Hamll. Band 34. N:o 8. T 



