92 CARBONIFEROUS CEPHALOPODA OF IRELAND. 



Affinities. — These are to all appearance with V. panclcarlnatas , but in the 

 absence of the septa they cannot be very well discussed. There are, however, 

 very decided differences between the two species, firstly, in the dimensions of the 

 peripheral area, which is much narrower in the present species than in V. paucl- 

 carinatus, and again in the height of the whorl, less dorso-ventrally in the former 

 species than in the latter, these features resulting in a much shallower umbilicus ; 

 secondly, in the character of the area formed by the umbilical margin and the 

 inner keel of the latter, as already described (cf. PI. XXIV, figs. 1 a, b). 

 The young individual figured upon PI. XXV (figs. 2 a, h) has some points 

 of resemblance with V. semiplicatus which cannot be overlooked ; these are 

 principally in the umbilical characters. Each has the shelf-like level area 

 included in the space between the edges of the umbilicus strongly keeled in the 

 young shell (cf. fig. 2 n) and the inner keel. No comparison can be made of the 

 features presented by the peripheral area, as this is seen only in the senile stage 

 of growth in V. semiplicatus. They are very strongly marked in the young 

 individual, consisting of two deep and conspicuous sulci bordering the central 

 zone, flanked upon the outside by two keels or ridges, the inner one, or that 

 bordering the sulcus, being much stronger than the outer one. The central zone, 

 which is slightly concave, is ridged on each side, the ridges, which are but slightly 

 raised, forming the inner boundary of the sulcus on each side. Judging from 

 numerous specimens of adult shells of Vestinautilus, it is probable that these 

 conspicuous ridges and sulci do not persist, but that they become gradually 

 obsolete as the shell progresses towards the adult stage. 



Bemarhs. — The conspicuous tubercular folds upon the body-chamber of the 

 present species would appear to be a senile chai'acter, the shell described showing 

 signs in the coarse and rugose appearance of its surface that it has reached an 

 advanced stage of growth. From the fact that only one specimen of this species 

 has been obtained up to the present time it must not be too readily assumed that 

 it is a rare one. The search on the occasion upon which the individual here 

 described was obtained was too limited to justify any such conclusion. This 

 part of the country has not had such attention bestowed upon it as the very 

 interesting nature of some of the material already collected there ought to 

 arouse. I hope something m.ay be done before long to work up the fossil fauna 

 of these rich south-western counties. The chief obstacle is the want of any local 

 interest in the subject. 



Locality. — Rathkeale, near Limerick. 



