OF THE SPECIES.

Ill

Occurs in very old strata of the transition limestone ; three different species are known,respecting which I beg to refer to the authors quoted.

1. A. nasutus, Dalm. Palcead. 54. 1 ; Emmr. Biss. 49. 1 ; Milne Edw. Or. iii, 296. 1 ;Boeck, Gaea Norm. 1, No. 47.

In a gray limestone of Eastgothland, at Skarpasen and Husbyfjol; occurs also in a redlimestone of the Billinger Mountain at Skofda.

2. A. mammittatus, Saks’ Isis, 1835, 335. 3, Table VIII, Fig. 4 ,a-c (the caudal shield d‘probably belongs to a Trinucleus); Emmr. Biss. 49. 2; Milne Edw. 1. c. 3; Boeck, l. c.No. 46.

Occurs in the transition limestone of Loadegaarts Oen, and Hjortnaestangen, nearChristiania.

3. A. rostratus, Sars , ibid. 334. 2, Table VIII, Fig. 3, a-e; Emmr. Biss. 49. 3; MilneEdw. ibid. 2; Boeck, ibid. No. 5.

Found at the same places with the preceding species, but more rarely.