cxii BRITTSTT GRAPTOLTTES. 



lg()1 Two questions of synonymy were discussed by Moberg in 



Moberg, 1891. The first deals with Dictyonema and Dictyograptus, 



" Om ett par Synouo- and Moberg urges the adoption of the latter name for the 



mier," ' Geol. Foren. same reason as that given by Hopkinson and Lapworth, 



namely, that Dictyonema is an " old-established name for a 



genus of plants." The second deals with Didymog. caduceus 



or D. gibberulus. As Salter's name, 77. caduceus, has been used for two species, 



and it is impossible to say to which of the two the original name corresponded, 



Moberg agrees w r ith Nicholson that it can no longer stand, and he proposes 



the general adoption of Nicholson's specific name, IK gibberulus. 



1892. Numerous papers dealing with Graptolites appeared in 



TSrnquist, 1802, the majority of them being by Swedish writers. 



' Siljansomr&dets Another part of Tornquist's great work on the " Siljan- 



Graptoliter,' pt. li. som radets Graptoliter " was published during this year. It 



deals wholly with the Monograptidae. The author discusses the three genera usually 



included under this family — viz. Cyrtograptus, Bastrites, and Monograptus, and 



classifies the various species belonging to the last-named genus, rejecting Jaekel's 



division of Mmiograptus into Pomatograptus and Pristiograpkis. 



Tornquist's classification is based on the principle adopted by Lapworth (187G) 

 — namely, on the form of the polypary and the form of the theca?, but it is 

 far more detailed. The proposed divisions are as follows : 



(a) Thecas tube-like, of prismatic form, with upper walls in contact 

 throughout. 



(1) Rhabdosome narrow, flexible; type M. Nilssoni. 



(2) Rhabdosome wide, rigid ; type M. Hisingeri. 

 (r.) Upper wall of theca partly free. 



(1) Rhabdosome straight or curved. 



(a) Theca with only a narrow border near the aperture free; apertures 



hook-shaped, pressed into the polypary (M. crenulatus, etc.). 

 (/>) Upper Avail of theca prolonged into a lip-shape, type M. priori on. 



(c) Outer part of theca bent round and grown to the lower walls 



(M. lobiferus). 



(d) Free part of theca bent round in a loop shape (M. sartorius). 



(e) Free part of theca bent double into an S-shape (M. nodifer). 



(/) Upper free wall of theca passing over without a boundary into 



the lower wall of the theca above (M. runcinatus). 

 (f/) Upper wall of theca prolonged into a long spine (M. Sedgwiclcii). 



(2) Polypary spirally curved. 



(a) Theca growing out centripetally (M. discus, etc.). 

 The main part of the paper is occupied with careful descriptions illustrated by 

 excellent figures, of numerous species of Monograptus, etc., some of the species 



