79 
Nicnoxtson called my attention to Parkeria, Carp., which no 
doubt shows structure which is also seen in M. Nicholsoni, 
but in the former there is a nucleus constituted of chambers 
which are laid end to end in a rectilineal direction, and sepa- 
rated by septa. Ihave not detected a nucleus of this nature 
in M. Nicholsoni. 
Another organism which especially struck Dr Hinper as 
similar to my new genus is Girvanella problematica, Nicu. and 
Eruer., jun. Professor Nicnouson has kindly sent me rock 
specimens containing that fossil, from which I have been 
enabled to get some good sections. As regards mode of occur- 
rence, there is a great resemblance with M. Nicholsoni, and 
also in the concentric lamination, but the minute structure is 
quite different. 
EXPLANATION OF 
PLATE ILLUSTRATING Mr WETHERED’S PAPER ON 
MITCHELDEANIA NICHOLSONI 
Fig. 1. Vertical section of a portion of the organism, showing 
large and small tubuli. x 45 diam. 
Fig. 2. Section of a small specimen of Mitcheldeania Nicholson 
above the surface of attachment. x 20 diam. 
Fig. 3. Portion of the upper part of Fig. 1. x 155 diam. 
Fig. 4. Tangential section, showing the smaller tubuli. x 155 
diam. 
Fig. 5. Section of a Zodidal tube. x 155 diam. 
Fig. 6. The minute canals which penetrate the skeleton fibre. 
x 155 diam. 
Tangential section, showing the larger, or zodidal, 
tubuli. x 45 diam. 
Fig. 8. Horizontal sections of the zodidal tubes. x 155 diam. 
= 
vi 
I 
HW ovu: 1887 
