-fi JOHAN KLBR. [sec. ARCT. EXP. FRAM 



M-ulpture and interior structure from the Psammosteus remains previously 

 described. In certain respects tliey are nearer to the well-known Drepanaspis 

 Gemi'mdenensis of Trauuair's description, but they cannot be combined 

 with that form. I will return to this matter subsequenth', and simply 

 state here m what manner the specimens described may be orientated. 

 I make the very probable assumption that Drepanaspis is a closely 

 related form, that provides us with a representation of the habits of the 

 body in the case of Psammosteus. 



The specimen descjuhed in 1 must therefore be assumed to be a 

 fragment of one of the large central body plates, either doi'sal or 

 ventral. 



The fragment desciibed in 2 probably belonged to one of the lateral 

 plates, as the denticles on these in the case of Drepanaspis are usually 

 extended. 



The little plate described in 5 shows signs of correspondance to the 

 small, intermediary plates in Drepanaspis. 



The fragment described in 4 is more difficult to determine. It is 

 evidently portion of an element with an oblique, spine-shaped construc- 

 tion, corresponding to those known from the Livland Psa)«»tOA'tet(S form. 

 It might be regarded as either a dorsal spine or a lateral spine, for the 

 posterior corners of the lateral flaps in these forms possibly emerged in 

 sharp spines or horns, instead of being bluntly pointed as in the case 

 of Drepanaspis. 



Horizon. All the remains in our possession of this form come 

 from the fish horizon in Skrap Valley. 



Psammosteus complicatus new species. 

 (PI. II, fig. S; PI. V, figs 1-3; PI. \T, figs 1-3). 



A number of Psammosteus fragments in my material prove to be 

 so different from the above and other forms described, both as regard^ 

 the interior and the exterior chai-acter, that they must be regarded as 

 a new species to which I have given the name complicatus. 



The following peculiarities appear to be most characteristic; 



1. The denticles vary greatly both in size and in form. On certain 

 plates — presumably the large body plates, — they are large, round, and 

 regular, with central top and distinct ribs; in others, — presumablv 

 portions of the corner plates (cornua) — they are small, flat, oval, or 

 rhombic, sometimes greatly extended and faintly ribbed. 



