7 
with larger pores. The interval between outer and 
inner wall without continuous septa and walls only 
connected by a very delicate scaffolding of cylindrical 
bars. Referring to Bornemann’s only species, the geno- 
type, Dictyocyathus tenerrimus, he says the cup is 
beaker-shaped, the spitz running into a cone. The rods 
of the scaffolding appear in cross section as round or 
oval points, in longitudinal section as more or less 
broken lines. 
Bornemann gives very sketchy drawings of a frag- 
mentary specimen, the clearest of which is copied 
” roughly here in Plate XLIII, Fig. 170. There is noth- 
ing inconsistent in his description and sketches with 
its being a member of the family we now have under 
consideration. From the presence in the genotype of 
what appear to be anastomising rods in the intervallum, 
and of a conical spitz, the generic name may be used 
to include other species having these characters. 
Dictyocyathus graphicus. 
(Protopharetra graphica Bedford) 
Spitzes of this species are shown in Plate XLIII, Fig. 
171, 172, 173. This spitz is of “Alphacyathus type,” 
but the simple radial bars in the intervallum soon give 
place to a mesh with vertical and tangential as. well 
as radial members. ‘As there is reason to believe that 
there are other. Pleospongia with a somewhat similar 
intervallar mesh in the adult, which do not grow from 
a spitz of “Alphacyathus type," ‚and therefore would 
not be included in the present order, it is difficult to. 
place adult fragments of which the spitz is not avail- 
able. It would thus be important to determine whether 
any characters can be found in the adult which might 
serve to distinguish such specimens. To clear up this 
point will require further research, so that any sug- 
gestions which can be made at present are only tentative. 
For example, regular and regularly arranged pores 
in outer and inner walls are in favor of this family as 
"against irregular reticular and compound-reticular, i.e., 
spongy walls. Also, simple pores to the inner walls 
as against large canals leading inwards and upwards 
into the central cavity. Again where the intervallar 
elements join the outer wall they are often seen in tan- 
gential section to have an arrangement “in quadra." 
See, for example, Fig. 173, upper part of sketch, also 
Plate XII, Fig. 58D and 60B; this may, perhaps, be a 
useful distinction. The presence or absence of a circu- 
larly striated pellis “plastered” (as it were) outside 
the outer wall is a confusing feature; it is seldom if 
ever found on the most regular archaeos (Ajacicyathus, 
etc.) and is common in the lower part of Metacyathina 
(e.g.. Plate XXX, Figs. 120C, 123A); on the other 
hand, it occurs on some Dictyocyathus 08 (e.g., Plate 
"XII, Figs. 58D, 60B). Its occurrence as a localised 
coat associated with (?) “Exocyathus” lamellae on a 
specimen of Metacoscinus (Plate XXXIV, Fig. 134) is 
. here suggestive ioe a parasitic or pathological Rendition 
73 
but, if so, it seems to have a preference for distinct 
though often widely-separated species. To this genus 
belong also apparently Dictyocyathus irregularis Taylor, 
robustus and quadruplex Bedford. 
Genus Spirillicyathus Bedford. 
These small forms, which appear to grow from a 
spitz of Alphacyathus type, present features inter- 
mediate between Dictyocyathus and the regular septate 
forms, having partial and rudimentary septa; the outer 
wall is more irregular than is usual in members of this 
order, (See our fourth memoir, p. 30). The small 
unidentified spitz shown in Plate XLIV, Fig. 174, in 
successive sections from 7/8 mm. to 5/16 mm. diame- 
ter, resembles this type. 
Genus Dokidocyathus Taylor. 
The genotype Dokidocyathus simplicissimus Taylor is 
a large, relatively common, very well-known and clearly 
defined type. The scattered simple rods connecting 
inner and outer walls are not circular, as in 4lphacya- 
thus, but extended longitudinally, forming, so to speak, 
very short widely spaced septa. Spitzes of this species 
are of the Alphacyathus type and are shown on Plate 
XLIV, Figs. 175, 176, 177. 
Another species, almost devoid of septal bars, 
Dokidocyathus nihilum Bedfoxd. 4 
is 
New Family Ajacicyathidae. 
For reasons which have been given above we pro- 
pose this family for the inclusion of the most charac- 
teristic group of regular septate archaeos, growing from. 
a spitz of Alphacyathus type—the group which has come 
to be spoken of in recent years as Archaeocyathus—a 
name which, it has been shown, cannot be used for 
them. From this family we edizio in particular, such 
related forms as trachealis with a highly specialised 
inner wall. The presence of either synapticulae or dis- 
sepiments as a normal feature of any species appears 
to indicate its exclusion from this and closely related 
families (though the possibility may have to be con- 
sidered of dissepiments occurring abnormally as a re- 
sult *of fracture and repair even in species of this 
family). 
New Genus Ajacicyathus. 
The genoty pe Ajacicyathus ajax (Archaeocyathus 
ajax Taylor) is fully described by Taylor. Outer wall 
delicate with extremely fine pores distributed regularly 
about 6 to the mm. Septa regularly arranged and 
numerous, with pores rather remote and small, irregu- 
lar rows of six or seven occurring in an intervallum. 
Inner wall rather solid with regularly arranged pores, 
3 to the mm.; some being “stirrup pores,” others not. 
As regards characters which might be considered 
when now or later the family comes to be subdivided 
into more numerous genera, the following may be sug- 
