Ford; and has not since been resuscitated. Walcott 
used for it the generic name Lihmophyllum and subse- ` 
quent writers Archaeocyathus. Seeing that rensselaericus 
is not completely defined in respect of anatomy and 
development and that it may have had dissepiments, it 
would not now be one’s choice as genotype if the 
choice were open, and Ford’s hesitancy leaves the choice 
open; it therefore seems inadvisable to resuscitate the 
genus unless for fluted species of a certain kind. 
Protocyathus rarus, Ford, 1878, is another small, 
fluted form. It has a specialised outer wall, with a 
single row of stirrup pores at the line of each septum. 
The generic name has since been abandoned, but might 
be reateritated usefully for species having this particular 
character. 
Taking all these names into consideration, it appears 
that up to the present no unequivocal generic name or 
genotype has been proposed for the most characteristic 
forms of regular Archaeos having straight septa, uni- 
formly porous and simple outer auti inner walls, devoid 
of synapticulae or dissepiments usually of regular conical 
"shape, without flutings, and growing Gr a simple 
normal spitz. Such an iÅrchaeo is Archaeocyathus ajax, 
Taylor; this species has also the practical advantage of 
being so plentiful and well-preserved that all points 
in its anatomy and growth can be elucidated and dupli- 
cates can readily be procured for distribution and 
comparison. 
We therefore propose the generic name Ajacicyathus 
for these forms, with Ajacicyathus ajax, Taylor, as 
genotype, and to adapt the same name in the correspond- 
ingly family and order, as Ajacicyathidae and Ajacicy- 
thina respectively. The order is based on the 
“character of the spitz and therefore includes not only 
many of the forms lately called “Archaeocyathus” but 
also some Dictocyathus, Dokidocyathus, and other forms. 
. The definition of the order Ajacicyathina is:— 
trader: Pleospongia growing from a spitz in the form 
of a simple conical tube, Closed below, within which 
arises almost immediately a porous inner wall connected 
to the tube by fadial rods. The tube becomes perforated 
to form a porous outer wall; the radial rods develop in 
some cases into a trabecular mesh, in others into regular 
` radial usually porous “septa? and/or transverse 
“tabulae.” 
Family Alphacyathidae. New Family. 
Genus Alphacyathus. New Genus. 
Growing from the same kind of spitz as Ajacicyathus 
are a number of species which do not develop straight 
radial septa, but retain in the adult what appears to “be 
the primitive condition, viz., a scaffolding of rods 
uniting the two walls. By far the simplest and most 
ہم 
"ocyathus macdonelli Bedford may be included here . 
2 
minute form of the kind we have seen is a single specimen 
described below as Alphacyathus zero; we prefer, how- 
ever, to make Alphacyathus anularis the genotype, as a 
fair number of specimens of this have been found. 
Alphacyathus zero. 
The single specimen found is figured in Plate XLIII, 
Fig. 168. Its extreme minuteness is shown by the fact 
that, although apparently a mature individual and not a 
mere spitz, its diameter at the upper end is only 14 mm., 
with an intervallum distance of about 4 mm. The 
length is about 6 mm. The extreme tip is not seen, 
but is so near that the diameter at the lower end is. 
only 4 mm. 
to the mm., regularly arranged in quincunx. 
outer wall pores are not seen. The two walls are 
connected by numerous simple rather irregular radial 
rods. 
New: Species. 
Alphacyathus anularis (Genotype). 
(Dictyocyathus anularis, Bedford.) 
The species is described in our second paper, see 
Plate XI, Fig. 55, and will serve, for the reasons just 
given, as genotype. An excellent specimen has now 
been found, complete to the tip of the spitz, and is 
shown in Plate XLIII, Fig. 109. This shows that the 
skeleton commences as a simple conical tube, closed at 
the lower end by a hemispherical cap. At 4 mm. 
diameter (b) radial rods are beginning to grow inwards 
from the wall and at 2/3 mm. diameter (c) the inner 
wall appears, and outer and inner wall-pores. For 
the most part the connections between the walls in the 
adult are simple radial rods, but there is a tendency 
for these to be united by a single tangential row of ` 
synapticulae to form incomplete horizontal platforms, a 
kind of forerunner of the tabulae of Coscinocyathus. 
This feature is specific and not essential to the genus, 
which may be defined as simple, regular Pleospongia 
consisting of inner and outer regularly porous walls 
united by. radial rods, circular in section, usually 
numerous and isolated but occasionally united by a 
single row of tangential synapticulae, growing from a | 
simple spitz of similar character. A spitz of this type 
will be here referred to for convenience as a “spitz of 
Alphacyathus type.” 
In the same genus is placed Alphacyathus simplex 
(=Dictyocyathus simplex Taylor), and Alphacyathus - 
robustus (= Dictyocyathus robustus Bedford). Dicty- | 
provisionally, though it is a larger form and of a more ' 
expanding conical shape, and, being founded on a. 
single, obscurely preserved KO in which walt 
pores are not seen, it is insufficiently known for iique 
N 
determination. 
. IK 
Genus Dictyocyathus Bornemann. _ ۱ 
Cup with 
Bornemann defined the genus as follows: 
 fine-pored outer wall and sieve-like inner wall pierced Y 
The inner wall has minute pores, about 8 - 
The 1 
