KONGL. SV. VET. AKADEMIENS HANDLINGAR. li.\M> 34. \:o 8. 37 



Agnostus Dalm. 



Pl. I Bg. 7. 



Agnostm glandiformis Ang. Although there is no1 fche slightest evidence of eyes 

 in this the largesl of its genus, nor any free hypostoma hitherto has been found, \ve maj 

 here give a little account of our researches into this species. The scantiness of materia] 

 forms a chief obstacle to our knowledge. Only three entire, rolled up specimens have 

 been found, and it is by sectioning and preparing such thai any hope can be entertained 

 to gain reliable results. 



A rolled up speeimen from Andrarum Scania was sectioned lengthwise. The tail- 

 pieee closed tight against the headshield, so there had been little chance for foreign mat- 

 ter to penetrate into the interiör whieh, however, is filled. CTose below the cephalic 

 shield there is a remarkable strueture, mostly resembling an elongated intestine with swel- 

 lings joined by more narrow duets and anteriorly the coherence is interrupted. As in 

 crustaceans and Arthropods in general the stomach and the intestine are situated on the 

 dorsal side of the body. there is nothing unlikely in assuming that this in reality jna\ 

 be the rernnants of the intestine. This may also be compared with the observation mad< 

 b)- Volborth in his memoir »Ueber die mit glatten Rumpfgliedern versehenen Trilobiten», 

 1863, p. 46, tab. 1 tig. 12 where the heart-tube probably is delineated. Barrande has 

 also given tigures of what he considers as the intestine in Trinueleus. 



Below this organ in Agnostos, there lies a section of a vaulted calcareous plate 

 with its eonvexitv turned against the dorsal side of the head shield, that is to say quite 

 the reverse what might have been expected if it had been the hypostoma in its true 

 position. This may, however, not be any objection against considering it as a sectioned 

 hypostoma, loosened from its connection with the cephalic shield, distnrbed in its original 

 position and turned round, when the shell beeame tilled with mud. At the distal end 

 there is a much distinct duplicature. 



Asaphus Bron<;\. 



The wellknown hypostoma of this genus has the same characteristic shape. though 

 more pronounced, as in Ptychopyge, with its posterior margin deeply indented, so as to 

 form two large, pointecl lobes. There is properly only one median field, surrounded by 

 Hat, lateral borders, continuing down into the posterior lobes, from which it is separated 

 through a shallow groove. The maciila; are situated in this groove, on each side of the 

 interiör börder of the central field. They are more or less prominent, but whatever their 

 form may be, their surface is always entirely smooth, lying well circumscribed amidsl 

 the surrounding terrace lines. 



The following list enumerates.all the species in this genus, of which previous authors 

 have delineated the tubercles, though they in the descriptions only in verv few instances 

 have mentioned their presence. 



K S V . Vet. A k;id. Ilmull. Hand :S4. \:r 8 5 



