Vol. 52.] FAUNA OF THE KEISLEY LIMESTONE. 413 



IlljEnus fallax, Holm. 



There is one specimen of a small pygidium in the Woodwardian 

 Museum which shows all the well-marked features of Holm's 

 I. fallax ' from the Ze/toia-Limestone of Dalecarlia. 



In the shape of the pygidium, the position of the fulcrum, and 

 the relative size and triangular outline of the axis, with the faint 

 ridge from its apex to the posterior border, it entirely agrees with 

 the Swedish specimens. 



millitn. 



Length of pygidium 6*0 



Breadth of do 8-5 



Length of axis 2*5 



Width of do 2-5 



A specimen of the hypostome of an Illcenus in the Carlisle 

 Museum closely agrees with that of this species figured by Holm 

 (op. cit. pi. vi. fig. 116). It is subquadrate in form with a swollen 

 central portion, and is truncated in front and obtusely pointed 

 behind. A border of regular width (except at the anterior lateral 

 angles, where it expands considerably, but is imperfectly preserved) 

 surrounds it. 



The posterior end of the swollen central portion is furnished with 

 a marginal band, as Holm shows. A few large granules also 

 ornament the surface of this central portion. 



LeDgth=5*5 millim. ; width=5*0 millim. 



Ill^nus Rcemeri, Yolb. 



Both the middle shield and the free cheek of this species are now 

 known from Keisley, but they had not previously been identified. 

 However, a comparison of our specimens with the figures and 

 descriptions of /. Roemeri (with which Holm 2 identifies the Swedish 

 species /. vivax 3 from the Leptama-Limestone) shows that the 

 identification is correct. The shape of the head-shield, the relative 

 size of the glabella, the course of the facial sutures, the position 

 and size of the eyes, the characters of the free cheek, and the 

 ornamentation exactly correspond. Two imperfect specimens of 

 hypostomes from Keisley also bear a very close resemblance to the 

 hypostome of this species as figured by Holm (Joe. cit.). In Eussia 

 I. Roemeri occurs in the Lyckholm zone. 



iLLiENUS CJECUS, Holm. 



A solitary broken specimen of a middle shield agrees so exactly 

 in all points with Holm's species /. coecus* from the Lyckholm 

 zone of the Island of Dago that I do not feel any hesitation in 



1 Holm, ' Svenska Arterna af Trilobitslagtet Illcenus] Bib. k. sv. Vet.-Akad. 

 Handl. vol. vii. (1882) no. 3, p. 82, pi. ii. figs. 15-20. 



a Holm, ' Ostbalt. Illaen.' Mem. Acad. Imp. Sci. St. Petersbourg, vol. xxxiii 

 (1886) no. 8, p. 125, pi. ix. figs. 4-14. 



3 ' Svenska Arterna lllmn! p. 74, pi. vi. figs. 1-7. 



* ' Ostbalt, Illaen.' p. 162, pi. xi. fig. 11 a-d. 



