Observations on the genus Rastrites and some allied species of Monograph! s. 



19 



foregoing species, but because of my unsatisfactory material, the question of their 

 relationship must be reserved for future researches. 



Monograptus amphibolus n. sp. 



. . PL III, figs. 1G— 21. 



A fairly complete specimen is represented in fig. 16. Commencing with a 

 short, faintly curved portion, bearing thecal on its convex side, the rhabdosome 

 soon makes a gentle turn, and continues in the opposite direction describing more 

 than half a circle, and, owing to a torsion, also in this division emitting thecœ 

 from the convex margin. The thecœ are in the proximal part isolated and per- 

 pendicular to the common canal, gradually increasing in length from 1 mm. to 1.7 

 mm. The thecse of the remaining part, again, remind us very much of those 

 characteristic of Monograptus convolutus His., but are shorter and devoid of reflexed 

 lobes. In other specimens the thecœ are placed on the concave side of the distal 

 division, as shown in fig. 17. Shorter fragments are delineated in figs. 18 and 19. 

 The various appearances displayed by this species indicate that the rhabdosome, 

 like that of the foregoing one, has originally formed a conical spiral. But for this 

 peculiarity, the species makes the impression of a starved Monograptus convolutus 

 or M. decipiens. 



Locality and horizon. Sweden: Monograptus amphibolus has, as yet, 

 been found only at Kongslena (Västergötland) in the zone of Monograptus turri- 

 culatus. It is not rare there. 



Monograptus convolutus H isinger. 

 PL III, figs. 22, 23. 



Having in previous memoirs given illustrations and detailed descriptions of 

 this species l ), I propose in this communication only to add some facts bearing 

 upon its supposed relation to the genus Rastrites. 



In Muechisons »Siluria», fourth edition (1867), we find, p. 61 (Fossils 12, 

 fig. 3), a graptolite delineated under the name of Rastrites pcregrinus, which, however, 

 must be referred either to Monograptus convolutus, or to a closely related form. In 

 a paper likewise published in 1867 I recorded the true Monograptus convolutus His. 

 as »Rastrites? convolutus»; and ten years later Linnarsson advanced the contention 

 that Hisinger's original of Prionotus convolutus was, in fact, identical with Bar- 

 rande's Rastrites peregrinus. Even Tüllberg, who in his often-cited paper »On 

 the (Iraptolites described by Hisinger and other Swedish authors* clearly made 

 out the true characters of Monograptus convolutus stated, nevertheless, that » Hi- 

 singer's type specimen is very like Rastrites peregrinus». From what is now 

 known about the two species, it is evident that they are widely separated from 



*) Toknquist, Undersökningar öfver Siljansområdets Graptoliter II; Acta Univ. Lundensis, 

 Tom. XXVIII, 1892; p. 30. — Researches into the Monograptidse of the Scanian Rastrites Beds, 

 K. Fysiogr. Sitllsk. Hand. Bd. 10 (Acta Univ. Lundensis, Tom. XXXV) 1899, p. 21. 



