74 
McLean . — On the Fossil Germs Sporocarpon. 
definition intended to cover all the known genera, but to lay down 
a stricter definition of one alone is less easy, if it is to be carried into any 
particularity. Nor is it a matter of much importance, if we bear in mind 
the reservations made above regarding the -status of the genus. 
Confining ourselves, then, to the widest generalities, the following 
is the taxonomic basis of the forms selected for description here. The 
description is, of course, subsidiary to that previously given for the group. 
Sporocarpon. 
Spherical or spheroidal organisms of minute but very variable size 
(0*03-0-35 mm.) ; without attachments, and surrounded by a stereomatic 
envelope composed of vesicles which may be radially or tangentially 
developed. These vesicles contained protoplasm and possessed the power 
of extension and development during the life of the organism. Reproduction 
as in the group as a whole. 
Without proposing to split the genus up into new genera it is a matter 
of convenience to subdivide it into sections, the better to exhibit the 
interrelationships of the species. 
These are as follows : 
Sporocarpon § Eu-sporocarpon (i) 
N. compaction. 
S. tabulation. 
S. Oidospora. 
§§ Fredaia (ii) 
S. elegans. 
§§§ Diadematis (iii) 
N. celluloston. 
§§§§ Sir ion (iv) 
S. asteroides. 
§§§§§ Perichoderma (v) 
S. pachyderma . 
In the classification originally proposed, only one subgenus, Pericho- 
derma , was recognized, including the three latter species as given above, 
but they are obviously so divergent that nothing much was thus to be 
gained in clarity over the integral genus Sporocarpon. Consequently it 
has seemed better now to subdivide them further, while retaining the old 
generic title for all. 
We will proceed to their description in order: 
§ Eu-sporocarpon. 
(i) N. compaction. Williamson/ Phil. Trans.’, pp. 169-349, 1878. 
I look upon this as the central and typical species, as it is the most 
generalized type, and the others can be satisfactorily regarded as declensions 
or modifications from this as a primitive form. 
