﻿Vol. 66.] THE OKDOVICIAX OF THE GLEXSAUL DISTRICT. 273 



Iii N. emarginula, Ang., as figured by Brogger 1 , a similar ornamenta- 

 tion of the test occurs. The other Russian ~ and Scandinavian 

 species are less closely allied to it. 



/ 



Xilefs armadillo, Dalman. (PI. XXII, figs. 1, 2 a & 2 b.) 



There is one head-shield from the deposit marked 62 in a fairly 

 perfect state of preservation, showing the entire glabella, the eye- 

 lobes, and the facial sutures, which may be referred without 

 hesitation to the species JVileus armadillo, Dalman. 3 It especially 

 resembles the specimen figured by Schmidt 4 from the Baltic 

 Provinces, the faint median keel and tubercle on the glabella being 

 distinct. Prof. Brogger 5 mentions that, in examples of the variety 

 depressm without the test, there is often visible a small tubercle 

 on a raised keel. Our specimen which shows these features is also 

 without the test, and thus agrees in all these respects. The other 

 typical characters of the head-shield of N. armadillo are sufficiently 

 exhibited. The species occurs typically in the Orthoceras and 

 •Cystidean Limestones of Scandinavia and in the expansus stage (B 6) 

 in the Baltic Provinces. 



The impression from the Shangort Beds, previously described as 

 Sym/phy&urus (?) or Nileus* may be assigned to the same species, as 

 our new specimen possesses all the missing features which rendered 

 the identification of this other fossil doubtful. 



Our specimen measures as follows : length of glabella= 14"5 milli- 

 metres, width of the same between the eyes = 13*0 mm. 



A pygidium from the limestone (361), measuring 12 mm. in length 

 and 21 mm. in width, may also be referred to JSileus armadillo. It 

 possesses the shape and characters of the form figured by F. Schmidt 7 

 from Stage B 2 6 in the Baltic Provinces, which agrees closely 

 with the variety depressus, Sars & Boeck. The broad axis is of 

 faint elevation, but distinctly defined and of an obtusely conical 

 shape, and it shows traces of three or four rings on its surface. The 

 border is rather broad, weakly concave, but not marked off by a 

 definite furrow from the rest of the lateral lobes. The surface of 

 the shell seems to be smooth. 



Dimensions. — Length of pygidium=12 millimetres; width of 

 the same=21 mm.; length of axis = 7 mm.; width of the same 

 = 7 mm. 



1 ; Die Silurischen Etagen 2 & 3' Christiania, 1882, p. 68 & pi. vii, %. 7 a ; 

 pi. viii, fig. 7 ; pi. xii, fig. 13. 



2 F. Schmidt, ' Eev. Ostbalt. Silur. Trilob.' pt. v, Lief. 2, Mem. Acad. Imp. 

 Sei. St. Petersb. ser. 8, vol. xii, no. 8 (1901) pp. 98-110. 



3 Dalman, ■ Palgead.' 1828, p. 49 & pi. iv, figs. 3 a-3 e. 



4 F. Schmidt, « Rev. 0=tbalt. Silur. Trilob.' pt. v, Lief. 3, Mem. Acad. Imp. 

 Sci. St, Petersb. ser. 8, vol. xiv, no. 10 (1904) p. 64 & pi. viii, fig. 13. 



5 ' Die Silurischen Etagen 2 & 3 ' Christiania, 1882, p. 62 & pi. vii, fig. 6 a. 



6 F. R. C. Reed, Quart. Journ. Geol. Soc. vol. lxv (1909) p. 150 & pi. vi, 

 fig. 12. 



7 F. Schmidt, op. supra cit. pi. viii, figs. 17 & 18. 



T 2 



