180 
G. W. Lee — Trepostomata. 
right angles to the surface. A few centrally perforated tabula? occur in the axial portion 
of the zooecia, but they are totally absent in the peripheral region—in the zooecia as well 
as in the mesopores. 
The ratio of axial region to diameter is 0 - 6 : 1. Tangential sections differ widely, 
according to whether they run through open or through partly closed mesopores. In the 
first case the mesopores appear as angular apertures separated by narrow partitions, 
while in the second case they appear as minute sub-circular holes in a mass of tissue. 
The illustrations in pi. xvi., figs. 19, 20, represent these two aspects of the same zoarium. 
The few acanthopores observed are very small and inconspicuous. 
Distribution. —A large specimen of limestone collected by Mr. J. Rhodes in the 
Trout Beck, below Dumblar Rigg, King Water, Cumberland [R. 2965], is entirely 
made up of colonies of D. nana , a rare instance of a rock-forming Trepostomatous 
Bryozoon. It has not come under notice from any other locality. 
Observation. —The small size and gregarious habit of this species distinguish it 
readily from the other species described here, to none of which it seems to bear 
any affinities. 
The original of pi. xvi., figs. 18-20, is preserved in the Collections of the Geological 
Survey in London, i 
Dyscritella multifida sp. nov. 
Plate XVI, figs. 13-15. 
Description. —In the two specimens that have come to hand the zoarium consists of 
solid cylindrical dichotomous branches 4 and 5 mm. in diameter respectively. The 
surface is not shown. 
Internal characters. The change of direction towards the periphery begins early 
and gradually, and the zooecia reach the surface without an abrupt bend. The axial 
region is extremely narrow, being about one-third of the diameter. In the peripheral 
region the walls are not appreciably thick : the repeated intercalation of numerous 
deep-set mesopores gives them a remarkably complex dendritic appearance in longitudinal 
sections. Tabulse are entirely wanting in both mesopores and zooecia. There are some 
forty zooecia along a distance of 1 cm. Seen in tangential sections, the zooecia as well as 
the mesopores have a sub-angular outline. They are interspersed with numerous very 
large and conspicuous acanthopores, much darker than the general tissue. 
