30 CARBONIFEROUS CEPHALOPODA OF IRELAND. 



Baud iii). The species occurs in several places in the British Isles, chief 

 among which are Closeburn in Dumfriesshire (the locality wheuce Sowerby's type 

 was obtained), and Castle Espie, county of Down, where specimens of this rather 

 common species occur of such a size as fully to justify the name given to it by 

 Sowerby. It has been found also at Orchard, near Glasgow, and at Bolland in 

 Yorkshire. 



The specimens of A. giganteum yielded by the Carboniferous rocks of Belgium 

 present the same differences when compared with A. insulare as do those of 

 Scotland and Ireland, of which the closer septa in the Belgian form is the most 

 important one. To this must be added the striated test described above, whose 

 presence might seem to have been strangely overlooked among the many specimens 

 of this form passing through the hands of paleontologists. I have not observed 

 the test, however, upon any of the specimens from Closeburn or Castle Espie, 

 whence most of the specimens to be seen in museums have come. It is not so 

 astonishing, therefore, that it should all along have been supposed that the species 

 had a smooth shell. 



I am indebted to the kindness of Prof. J. Joly, F.R.S., for the use of some 

 examples of this species from the museum of Trinity College, Dublin. These 

 show the structures of the siphuncle remarkably well, considering the highly 

 crystalline condition of the rock in which they are preserved (PI. IX, figs. 2 a — c). 



Locality. — Castle Espie, county of Down (specimens figured). Other localities 

 are mentioned above. 



Actinooeras insulare, sp. nov. Plate X, figs. 1 a — d. 



Description. — Shell (fragment) large, straight. Section elliptical, at least in 

 the lower half of the specimen, the ratio of the two diameters here being as 

 53:48. Rate of increase about 1 in 7. Septa very concave, increasing rather 

 rapidly in their distance apart ; that is, at a place where the diameter of the shell 

 is 58 mm. they are 17 mm. apart, and where this has increased to 125 mm. they 

 are 35 mm. distant. The length of the portion of the shell thus measured is 

 260 mm., out of a total length of 345 mm. for the whole fragment. The septa 

 are strongly oblique in the upper part of the shell, where they have been exposed 

 by the accidental removal of the test in breaking the rock away from the shell ; 

 in the lower half they cannot be seen, as the test is there preserved and covers 

 them. Their obliquity makes an angle of about 20° with the horizontal axis of 

 the shell. The siphuncle is well seen in longitudinal (polished) sections (PI. X, 

 fig. 1 d), and its position is also indicated on the convex surface of the smaller 

 end of the specimen (PI. X, fig. 1 b). It forms, as usual with Actinoceras, sac- 



