170 
NATITTLOIDEA. 
surface of the test appears to be smooth, or marked only with very 
fine and obscure lines of growth. One of the specimens (Iso. 1G93) 
shows the scar of a portion of the sheU-muscle upon the cast of 
the body-chamber. 
Remarks. As Phillips described three species under the name 
Nautilus dorsalis, it is necessary to define them. The first described 
by him, as var. a, I propose to take as Nautilus dorsalis, that being 
the figured one. Phillips’s var. ft, with an angular umbilicus, I 
shall describe under the name Hibernicus ; while for the third, var. y, 
which is probably represented by de Koninck’s dorsalis, another Ji 
name would be required. I can find nothing to represent this f 
species among the British Museum specimens. [ 
It was long ago remarked by Portlock ^ that “ some of the varie- !' 
ties [of N. dorsalis'] mentioned by Phillips are really distinct species;” 
and de Koninck also pointed out the distinctness of Phillips’s [ 
varieties and regretted that that author had not applied different ( 
names to them. The specimen figured by Phillips, now in the 
British Museum, must, however, be adopted as the type of S. dor- !; 
salis, and not the variety y which M. de Koninck selected. [ 
Solenoclieilus dorsalis, as now restricted, differs from var. yin having [ 
fewer whorls, smaller umbilicus, and much more distant septa ; 
while it is readily distinguished from S. Hibernicus (=var. ft) by 
its rounded, instead of angular umbilicus. i 
Horizon. Carboniferous Limestone. [ 
Localities. BoUand, Yorkshire ; Kildare ; Blackrock, Bathfarlane, | 
near Dublin. | 
Well represented in the Collection, which includes the specimens | 
figured by Phillips in the ‘ Geology of Yorkshire,’ both of which i 
are in the Gilbertson Collection.” Of these No. C. 2971 is here j 
figured (fig. 27 j. j 
I 
I 
Solenocheilus Hibernicus, Poord. j 
1836. Nautilus dorsalis (var. jS), Phillips, Geol. of Yorkshire, pt. ii. | 
p. 231. I 
/Sp. Char. Shell Kautilus-like, tumid, very rapidly expanding, j 
consisting of about two whorls. The umbilicus deep, with very j 
steep sides, having an angular border (as shown in the figure). j 
There is a large central perforation. * 
The septa are somewhat wide apart, and the siphuncle is situated j 
Geology of Londonderry, 1843, p. 405. 
