C. Lapivorth — 0)i Scottish Monograptidce. 313 



science, these forms must be united under some distinctive title. 

 Whether the group thus constituted has a generic or subgeneric 

 vakie must be left for future determination. In the actual state of 

 our knowledge it may most conveniently be retained as the genus 

 B,astrites. 



M. Barrande never appears to have seen the virgida (solid 

 axis) in this genus, but to have inferred its existence from analogy 

 alone. Nor has it been mentioned as visible by any subsequent 

 observer. On the other hand, its apparent absence has been 

 remarked. In Plate X. Fig. 1, is figured an example of Bastrites 

 peregrinns, Barr., in which the virgula is prolonged as a naked 

 filament beyond the distal extremity of the polypary. Its presence 

 in the genus is thus placed beyond dispute. 



1. Rastrites peregrinus, Barrande. Plate X. Figs. 1 and 5. 

 Bdstrites peregrinns, Barrande ; Grapt. de Boheme, plate iv. 



figs. 3 and 6. Harkness, Quart. Journ. Geol. Soc. vol. vii. 

 plate i. fig. 1. Nicholson, Quart. Journ. Geol. Soc. vol. xxiv. 

 plate xix. figs. 23 and 24. 

 Monograpsus perep-inus, Geinitz ; Die Graptolithen, Taf. v. figs. 

 11 and 12. Richter, Zeitschrift d. Deutschen Gesellsch. 

 1853, Taf. xii. figs. 29, 30, 31. 

 Rastrites Linncei, Barrande ; Grapt. de Boheme, plate iv. fig. 3. 

 The foregoing list embraces references to all the more important 

 figures of this very well-known species, in what may be regarded 

 as its typical aspect. In addition to the type form, the Scottish 

 rocks also afibrd the following well-marked variety. 



Var. HYBRiDus. Plate X. Fig. 5. 



Monograpsus Linncei, Geinitz ; Die Graptolithen, Taf. v. fig. 10 

 a, h. 



Polypary about one inch in length, arcuate, incurved. Hydrothecse 

 16 to 20 to the inch, and about twice as long as the interspaces. In 

 this variety the interspaces are larger than in the typical form ; the 

 hydrothecse are shorter, slightly inclined, and frequently have their 

 apices reflexed. 



Locality. — Typical form, found everywhere in the upper zones 

 of the Birkhill Shales at Dobbs Linn, Craigmichan, Dumbreddan, 

 etc. Var. hyhridus is confined to the highest zones of the same 

 formation. 



2. Rastrites maximus, Carr. 



Bastrites maximus, Carruthers; Geol. Mag. 1868, Vol. V. Plate V. 

 Fig. 14. 



Locality. — Common in the highest beds of the Birkhill Shales at 

 Mountbenger Burn, Dobbs Linn, Garple, Frenchland, etc. 



3. Rastrites dtstans, sp. nov. Plate X. Figs. 2 a, h. 

 Bastrites Linncei, Nicholson ; Quart. Journ. Geol. Soc. vol. xxiv. 



plate xix. figs. 25 and 26. 

 Polypary filiform, one to two inches in length, straight or but 

 slightly curved. Hydrothecse isolated, perpendicular to the general 



