lxxxviii BRITISH GRAPTOLITES. 



1876. 

 Lapworth, ^ n 1876 Lapworth described in detail the various species 



" On Scottish Mono- of Scottish Monograptidas, revising the synonymy and classi- 



graptidse," ' Greol. fication, and figuring the species, many of which were new. 

 Mag.,' dec. 2, vol. iii. 



Synonymy. — Four genera are included in the family of the Monograptidas, 

 Monograptus, Oyrtograptus, and Rastrites, and a new genus Dimorphograptus. 

 The author discusses at some length the respective merits of the generic names 

 Graptolithus, Monoprion, and Monograptus, for those unilateral Graptoloidea in 

 which the thecas are in contact with one another, and decides in favour of Mono- 

 graptus. He retains the genus Rastrites, and notes the presence of the virgula in 

 this genus. 



Development. — The development of the Monograptida3 is here stated to be 

 similar to that of the bilateral Graptoloidea, but " the polypary originates from 

 a point near the broad end of the sicula," and " grows backward along the distal 

 portion of the sicula itself, to which it adheres." He considers it " probable that 

 all the Graptoloidea ought to be regarded as colonies of sicula?, held together by a 

 common body." 



Description of Sjjccies. — The following species are described and figured, and 

 the localities and ranges of each are given. 



Genus Rastrites. — (1) R. peregrinus, (2) R. capillaris, (3) U. maximus, (4) R. 

 distans, (5) R. peregrinus var. hybridus. 

 Genus Monograptus •. 



Group I. — Type M. Nilssoni. (6) M. Nilssoni, (7) M. intermedins, and (8) 

 var. involutus, (0) M. gregarius, (10) M. attenuates, (11) M. Salteri, (12) 

 M. argutus, (13) M. tenuis, (14) M. Sandersoni, (15) M. concinnus. 



Group II. — Type M. Hisingeri, (16) M. Uisingeri and (17) var. jaculum, 

 (18) M. cyphus, (19) M. leptotheca, (20) M. vomerinvs. 



Group III.— Type M. Halli. (21) M. Ilalli, (22) M. Riccartonensis, (23) M. 

 galaensis, (24) M. priodon, (25) M. Flemingii, (26) M. colonus, (27) var. dubius. 



Group IV.— Type M. SedgwicMi. (28) M. Sedgwickii, (29) M. convolutus, (30) 

 var. (a) communis, (31) (b) fimbriates, (32) (c) proteus, (33) (d) spiralis, (34) M. 

 triangnlatus, (35) M. turriculatus. 



Group V.— Type M. lobiferus. (3.6) M. lobiferus, (37) M. Becki, (38) M. 

 Clingani, (39) M. runcinatus, (40) M. Barrandei, (41) M. exiguus, (42) M. crispus. 

 Genus Gyrtograptus. — (43) C. Carruthersi, (41) ('. Grayi. 

 Genus Dimorphograptus. — (45) D. elongatus and (40) ]). Swanstoni. 

 The discovery of the genus Dimorphograptus, intermediate between Monograptus 

 and Diplograptus, led Lapworth to abandon his former theory that in Diplograptus, 

 etc., the sicula gave origin to two buds, and to suggest a simpler one. " According 

 to this new theory the sicula in nil the Graptoloidea throws off a single bud 



