Vol. 69.] THE GENTJS AULOPHYLLUM. 71 



Bathgate material, and I need only emphasize the great diversity 

 in character and the high stage of development attained by many 

 individuals. 



(b) Northumberland and Durham. — The forms from 

 Northumberland and adjoining counties share these characters. 

 The material received from the neighbourhood of Scremerston, 

 near Berwick-upon-Tweed, mainly consisted of small forms, the 

 central columns of which were of the ' rose ' type. 



From the Thornbrough Limestone near Corbridge I have col- 

 lected some large forms in which the septal lamellae, though well 

 developed, were comparatively few in number (PI. VII, fig. 1). 

 At this and adjacent horizons smaller forms which closely re- 

 semble the larger forms are also abundant ; but the reduced size of 

 the central column causes the septal lamellae to be more crowded, 

 and hence the tissue presents a denser character (PI. VII, fig. 2). 



An interesting type is particularly characteristic of the Great 

 Limestone of Weardale. The septa are numerous, and the outer 

 dissepiments fine. The central column is small in comparison with 

 the size of the corallum ; but the septal lamella) are very numerous 

 and remarkably straight until coalescence takes place, although this 

 does not occur until the lamellae have passed some distance into 

 the central column. The resultant principal lamella? are sinuous 

 in habit ; in some cases they reach the centre of the column, in 

 others leave clear a central space of the ' rose ' type. The longi- 

 tudinal section shows a dense mass of fine central vesicles and long 

 closely-set pericentral vesicles (PI. VII, tigs. 3 a, 3 b, & 4). 



The ' rose ' form illustrated in PI. VII (fig. 5) was obtained 

 from the Great Limestone at Chollerford, near the confluence 

 between the North and the South Tyne. It is remarkable on 

 account of the shortness of both the major and the minor septa, the 

 latter being very feebly developed. 



(c) The Craven district and the country around More- 

 cambe Bay. — The examination of the sections cut at Stage D 

 suggests that most of the forms from these localities are descended 

 from mut. tenbiense rather than from redesdalense. Moreover, the 

 form described as mut. cumbriense retains the tenbiense character. 

 Forms approaching mut. pacliyendoiliecum are common, but none 

 that I have yet examined attain the highest development of the 

 more northern forms. 



(d) Anglesey and North "Wales. — The material from Angle- 

 sey and North Wales includes forms comparable with the Bathgate 

 varieties (PI. VIII, figs. 5 & 6 o), having long, well-developed 

 septal lamellae ; but they usually show the tenbiense character at 

 Stage 1) (PI. VIII, fig. 6 a). Others agree more closely with 

 mut. cumbriense. 



(e) Mendip Hills. — Some specimens from the Mendip Hills 

 appear to be little advanced upon mut. tenbiense ; they are in too 

 poor a state of preservation to be described with any certainty. 



