titions, but has, centrally, in the upper part a kind of 
crude, irregular inner wall. 
New Species Archaeopharetra tenuis. 
This form, which has a more delicate, crowded tissue, 
is shown in Figs. 121 A, B, C. A tangential section just 
within the wall shows a certain degree of orientation of 
the structural elements. There is no sign of an inner 
wall. 
New Species Archaeopharetra syrinx. 
This interesting modification is shown in Fig. 122 A, B. 
The more or less horizontal partitions are united by 
more or less vertical columns of perforated plates, form- 
ing a cellular structure with perforated dividing walls. 
This is possibly a spitz of “Syringocnema.” 
H 
Archaeopharetra sp. 
The specimen shown in Fig, 123 A, B commences as 
a fine tube with the usual horizontal partitions and 
continues as a rapidly expanding cone, with development 
of trabecular tissue and change of orientation of the 
originally horizontal partitions. This is evidently the 
spitz of a form near Metacyathus. 
“Archaeopharetra” and the Metacyathina. 
The character of the “Archaeopharetra” spitz, differing 
entirely as it does from other Archaeo spitzes, is strong 
justification for the establishment of the Order Meta-. 
eyathina; and present indications point to increase in 
the number of forms which may have to be included in 
this order, Among genera which have already been 
included in the order and whose inclusion is now 
receiving confirmation are Metaidetes, Metacyathus, and 
Metacoscinus; but there are also forms hitherto classed 
by us as “Spirocyathina” which may have to be included 
among the Metacyathina; one such is Syringocnema, 
and we have also seen fragments with an Archaeo- 
pharetra-like base passing upwards into an undetermined 
“Spirocyathus”-like cup. Further material is necessary 
lo clear up the position as regards individual genera. 
On the other hand, it is quite clear that not all 
“Spirocyathina” have to be transferred to the 
Metacyathina; for example, we have recently found an 
excellently preserved specimen of Protopharetra 
graphica in which the minute spitz plainly shows the 
normal features of porous outer and inner walls con- 
nected by trabecular mesh. 
_In mature cups of the Metacyathina it would appear 
that the dissepiments, which are a frequent feature, have 
probably arisen by persistence, with changed orientation, 
of the horizontal partitions of the “Archaeopharetra” 
spitz. The trabecular structures, including septa, inner 
wall and synapticulae appear to have arisen from the 
vertical rods which begin to appear as growths on the 
partitions at a little distance above the spitz. Not all 
mature cups of Metacyathina show dissepiments; these 
for the most part are lost in the upper parts of 
Metaldetes and Metacoscinus; even in some specimens 
of “Archaeopharetra” such as that figured 120 A it will 
31 
be noticed that the horizontal partitions are confined to 
the extreme spitz. 
New Species Metacyathus ramulosus. 
A well-preserved fragment of one of the Metacyathina 
is shown in Fig. 124 A, B. The presence of fairly 
numerous dissepiments corresponds to our definition of 
the genus Metacyathus, but the specimen does not quite 
coincide with either of the previously described species. 
It is more like the unnamed specimen figured in Plate V, 
Fig. 28, which we compared to Metaldetes. The frag- 
ment is of a large cup, 8 or more cm. diameter; the 
intervallum is 9 mm. The outer wall appears to be a 
coarse mesh with tubercules encroaching on and partly 
subdividing the “pores.” The septa are a full mm. 
apart aud have fairly uniform circular or oval pores, 
about 1/3 mm. diameter and three to 2 mm. Curved 
dissepiments are present. The inner wall, which is seen 
from the septal side in Fig. 124 A is a beautiful example 
of “compound reticular” structure, being composed ot 
a coarse irregular mesh attached to the septa and bearing 
a fine reticular mesh on its inner face. We name it 
M. ramulosus from the character of the inner wall. 
New Genus Ardrossacyathus. 
The genus is founded on a single unsilicified fragment 
from Ardrossan to include Metacyathina with irregular 
outer wall, dissepiments, porous inner wall, and 
endothecal tissue showing a horizontal stratification 
reminiscent of Archaeopharetra tenuis. The genotype, 
A. endotheca, possesses straight septa of delicate open 
mesh. 
New Species Ardrossacyathus endotheca: 
The fragment indicates an intervallum coefficient 
4 mm. : 5 mm. The outer wall appears to be irregularly 
porous. The septa are straight, a mm. apart, composed 
of a delicate mesh surrounding polygonal pores four to 
l mm. The inner wall is thin with rather irregular 
pores about four to 1 mm. The endothecal tissue is to a 
considerable extent aggregated to form curved transverse 
irregular sheets, running acros$ the central cavity and 
spaced about 3 mm. apart. See Plates XXX, Fig. 125 A 
and XXXI, Fig, 125. 
x Compare Ardrossacyathus. 
Another unsilicified fragment from Ardrossan is shown 
in oblique transverse section in Plate XXI, Fig. 126. 
If the tissue at the top left corner and lower left side of 
the sketch represents outer wall, it is very rugged and 
irregular. There is a definite porous inner wall and 
the central cavity is filled with endothecal tissue in 
layers resembling that of Ardrossacyathus. The inter- 
vallar tissue, however, is much more irregular than that 
of A. endotheca. 
New Genus Metaldetimorpha. 
We propose this generic name for some very obscure 
and shapeless fragments which are fairly frequent in the 
Ardrossan limestone; another obscure form occurs at the 
“Paint Mine,” Beltana. Genotype, M. yorkei. 
