310 C. Lapivorth — On Scottish Moiiograptidce. 



base of the overlying Gala Group, and in tlie equivalent strata of the 

 neighbourhood of Girvan. In the later Hawick beds none have 

 been detected ; but they again occur in great numbers, but in very 

 indifferent preservation, in the Eiccarton beds, and a few examples 

 have been procured from the Wenlock strata of the Pentland Hills. 



These Scottish species, with but few exceptions, are found in 

 equivalent strata in other districts. Many, however, are as yet 

 confined to the Silurian deposits of the British Isles. 



5. Synonymy. — The species here classed in the genera Rastrites 

 and Monograptus, together with several other genera, were placed 

 originally in the genus Graptolitlius of Linnseus — a title subsequently 

 modified by Beck and Murchison into GraptoUtes. The first 

 improvement in classification was made by Professor M'Coy, who 

 separated the diprionidian forms under the title Diplograpsis 

 (afterwards altered to JDiplograpsus) . Unaware of M'Coy's pro- 

 cedure, M. Barrande eliminated from Graptolitlius the two genera 

 Retiolites and Rastrites, and divided the remaining forms into two 

 subgenera — Monoprion and Diprion. Kecognizing the validity of 

 M'Coy's genus Diplograpsus, and following out his principle of 

 nomenclature, Professor Geinitz next proposed the title of Mono- 

 graptus for the forms included by Barrande under Monoprion and 

 Rastrites — uniting these groups on the ground of their being 

 connected by an intermediate species. 



Herr Eichter is almost the only observer who has strictly followed 

 Geinitz. British palaeontologists recognize the genus Rastrites, and 

 class the forms which Barrande grouped in his subgenus Monoprion 

 under the old generic title of Graptolitlius. 



There are several strong objections to the employment of the 

 primitive title in this restricted sense. In the first place, it is more 

 than doubtful if either of the species described by Linnaeus as 

 Graptolitlius belonged to this group. Again, the title has been 

 employed in turn for almost all the genera of the RJiabdophora ; — 

 from Climacograptus, to which it has been asserted it was applied by 

 its founder, — to the comparatively recently discovered family of the 

 DicJiograptidcB, to the highly compound forms of which it is 

 applied by Professor Hall. At the same time it is in daily use as a 

 general title for all unplaced GraptolitJiina — an application of the 

 term so simple and convenient that no field geologist would consent 

 to relinquish it. It is consequently impossible to avoid ambiguity 

 unless we employ a different title for the group in question. 



There are two candidates for the post — Monoprion of Barrande 

 and Monograptus of Geinitz. 



The genus Graptolitlius as described by Barrande did not include 

 any branching forms, and consequently his subgenus Monoprion em- 

 braces exactly the same species classed by Carruthers or Nicholson 

 in the curtailed genus Graptolitlius. In strict justice, Barrande's 

 term should be allowed to stand. It has, however, been subsequently 

 modified to designate a complete division of the Graptolithina,^ and 

 has apparently been relinquished by its founder himself.^ 



^ Hopkinson, Journ. Queckett Micros. Club, vol. i. no. 6, page 8. 

 2 Deiense des Colonies, vol. iv. pp. 133, 25, etc. 



