Vol. 54.] FATJlfA. OF THE 8KIDDAW SLATES. 469 



Fam. I^EMAGRAPTiD^, Hopk. 



Genus Leptograptus, Lapw. 

 Sp. L. sp. 



Fam. D1CRAN0GRA.PTID.E, Lapw. 



Genus Dicellograptus, Hopk. 



Sp. D. moffatensis (Carp.). 



Fam. DiPLOGRAPTiD^E, Lapw. 



Genus \. Diplograptus, M'Ooy. 



Sp. (a) B. dentatus (Brongn.) 

 (b) D. teretkisculus (His.) 

 (e) D. appendiculatus,''' Tornq. MS. 

 Genus 2. Climacograptus, Hall. 



Sp. CI. Scharenbergi, Lapw, 

 Genus 3. Cryptograptus, Lapw, 



Sp. (a) Cr. Hopkinsoni (Nich.). 



(b) Cr. antennarius, Hall. 



(c) Cr. tricornis (Carr.). 



Fam. Glossograptid^e, Lapw. 



Genus Glossograptus, Eramons. 



Sp. (a) Gl. armatus (Nich.). 



(b) Gl. Hinckm (HopkV 



(c) Gl. fimbriatus (HoTpk.). 

 Fam. Ebtiolitid.e, Lapw. 



Genus Trigonograptus, Nich. 



Sp. (a) Tr. ensiformis (Hall), 

 (b) Tr. lanceolatus, Nich. 

 Fam.? 



Genus Thamnograj^tus, Wxch. 



Sp. Th. Boveri, Nich. 



III. Description" of Geneea and Species. 



Genus Bryograptus, Lapw. 



(6) Brtograpttjs Kjerflfi, Lapw. (I'ig. 1, p. 470.) 



1880. Br. KjerulJi,li2Lpw. Ann. Mag. Nat. Hist. ser. 5, vol. v, p. 164 & pi. v, 

 fig. 22. 



1882. Br. Kjeruljl, Brogger, ' Die silur. Etagen 2 u. 3 im Christiania-Gebiet,' p. 37 

 & pi. xii, fig. 20a. 



* The rhabdosoma consists of two slender primary stipes diverging 

 from a conspicuous sicula at a small angle. From the inner margin 

 of these there originate two or more compound secondary stipes. 

 These are symmetrically disposed, and the earliest ones arise near 

 the sicula. The thecse number twenty to the inch (eight in 10 mm.) ; 

 they overlap for less than one-third of their length, and are inclined 

 at an angle of about 20°. Their outer walls are curved, and the cells 

 widen slightly in the direction of the aperture, which is concave. 

 The apertural angle is about 110°.' 



The sicula of this species is decidedly large, being commonly J-g- 

 inch in length (about 1*5 mm.). From its apex a fine thread-like 

 prolongation is often seen to extend ; this is without doubt the 

 virgula (' nema ' of Lapworth). 



Lapworth gives the angle of divergence of this species as 40^ 

 but it often appears larger, owing to the mode of pre servation of the 

 form. 



