Studies in the Hchinoidea. No. XI. 4.25 
lines on each plate But the extreme smallness of the primary 
tubercles of the adapical surface, and the wealth of simple secondary 
tuberculation and granulation there, coupled with the rapid increase 
in size of the primaries at and orad to the ambitus, are of such a 
quality that Holectypus rather than Conulus (still more than Pyrina) 
affords the nearest comparison. But such a character (indicative 
of difference in size of the radioles on the two surfaces) is more likely 
to be adaptive than intrinsic, and so can hardly be invoked as 
involving close affinity. Again, the shape, size, and position of the 
periproct are all comparable with those features in Holectypus. 
The points of chief importance wherein Conulopyrina differs from 
all other Echinonéide (sensu meo) are: the prolongation of triserial 
arrangement of the podial pores over the entire adoral extent of 
the ambulacra, the position of the periproct (roughly intermediate 
between Conulus and Pyrina), and the quality and pattern of the 
surface ornament of both areas. Pzleus is the only Holectypoid 
in which the pore-pairs show comparable departure from the 
uniserial plan (both in quality and extent), but there is no other 
apparent reason for suggesting any close relationship between the 
two genera. The position of the periproct is certainly suggestive 
of a stage midway between Pyrina and Conulus, but the known 
migration of this aperture in ontogeny makes it unsafe to give 
Conulopyrina such a phyletic place, since only one example is 
available. It is, however, far from impossible that this may be its 
true interpretation. 
The order of appearance and disappearance of the main tubercle- 
rows on the ambulacra is very strange. That the primordial con- 
tinuous row should be external (adradiad) is normal for the order, 
although the reduction of its members to almost secondary rank 
on the adoral surface is unusual. The situation of the second row 
on the alteruate primaries is normal, but the disappearance of this 
series adapically while the third row still persists is quite anomalous. 
The arrangement of the interradial primary tubercles is fairly 
typical of that found in Anorthopygus or Pyrina, but there are 
more unituberculate plates than is usual in the Echinonéide. 
However, the extraordinary congestion of the minor ornament on 
the adapical surface, coupled with the great reduction in size of 
the primaries in that region, seem unique for the Holectypoida, 
and can best be compared with the granulation of such Caratomids 
as Conulopsis (““ Echinoconus”’ of Lambert). This comparison is 
emphasized by the maintenance of sunken areole in the reduced 
apicad tubercles; but I should hesitate to suggest any phyletic 
meaning in the character, especially in view of the great contrast 
in ambulacral structure between Conulopyrina and Caratomus. 
To sum up, Conulopyrina is definitely a member of the Echinonéidee 
(as I interpret the family). It is neither a Conulus nor a Pyrina ; 
it possesses-some of the characters of both these groups, and others 
present in neither. Its resemblance to Holectypus is most probably 
