ACTrN^OCE:RATID^. 
Sp. Char. Shell straight. Eate of tapering not ascertainable in 
the t}*pe specimen, owing to its imperfect state. The septa are 
strongly arched, and distant ahont J an inch, where the diameter 
measures about 2 inches. The siphuncle, which is very much dis- 
torted or pushed out of place, is strongly inflated between the septa, 
so as to form a series of cushion-like bulbs, whose greatest trans- 
verse diameter is a little above the centre, so that the upper part of 
each element is a little more inflated above than below. Surface 
characters unknown. 
Remarks. Through an oversight, only a portion of the specimen 
in the British ITuseum was figured by Prof. Blake, but the remainder 
adds very little to our information respecting the species. Each 
element of the siphuncle is marked by a series of longitudinal folds, 
which give it a wrinkled appearance. 1 regard this species as clearly 
distinct from Actinoceras coclileatum, and in this view Dr. Lindstrom 
coincides with me. In the latter the elements of the siphuncle are 
much broader and more depressed than they are in A. Blakei ; so 
that the ratio of the vertical and transverse diameters is as 9 : 26, 
while in the latter it is as 5 : 10. The siphuncle, in fact, occupies 
a much smaller space in the shell in A. Blakei than it does in 
A. cochleatum. 
Horizon. Upper Llandoveiy ^ ? 
Locality. Gwernyfed, near Builth, on the borders of Eadnorshire 
and Brecknockshire. 
Eepresented in the Collection by the specimen figured by Blake 
{loc. cit.). 
^ Prof. Blake records this species from the Lower Silurian [Ordovician], 
doubtless on the authority of the label affixed to the specimen, which reads 
“ L. Silurian.” Entertaining considerable doubt as to the correctness of this 
view, I wrote to Mr. Clement Eeid, of the Geological Survey, and be kindly 
forwarded my letter to his colleague, Mr. Aubrey Strahan, who is well acquainted 
with the district whence the specimen was obtained. That gentleman informs 
me in reply, that “ Gwernyfed is situated on a very narrow band of Upper 
Llandovery,” and that “immediately to the N.W. lies the Wenlock Shale, and 
to the S.E. the Llandeilo Flags adding, “ it would be impossible to determine 
the age of your fossil xmless the pit from which it was obtained could be iden- 
tified.” 
However, taking into consideration the fact that all the British examples of 
Actinoceras (with the exception of A. mendax from the Durness Limestone) have 
been found in Silurian strata, and the appearance of the fossil in question sug- 
gesting that horizon for it, I have assigned it provisionally thereto. 
N 
