VESTINAUTILUS CRATERIFORMIS. 85 



The specimen before me is much distorted, and part of tlie body-cbamber is 

 wanting. The umbilicus on one side is partly clear of the matrix, so that it 

 reveals a portion of the penultimate whorl. Only part of the test is present, but 

 there is sufficient to show that the keel bordering the umbilicus is not well defined, 

 and that it becomes obsolete on reaching the body-chamber, the shell becoming 

 more and more broadly rounded on the umbilical margin as the region of the 

 aperture is approached. The outlines of the sutures of the septa are irregular 

 owing to the crushing the shell has been subjected to, but it can be seen that they 

 formed a shallow sinus in the median line of the periphery. The distance of the 

 septa from each other in the latter position is 10 mm., close to the base of the 

 body-chamber; the fourth and fifth, counting from the latter, measuring 9 mm., 

 the seventh and eighth 7"5 mm. (cf. V. carlnlferus, PI. XXIII, fig. 2). 



Dimensions 



Specimen in Museum of Science 

 and Art, Dublin. 



Diameter of shell (approximate) . . .73 mm. 



Width of umbilicus, about . . . . 52 „ 



„ periphery . ... . 52 „ 



Height of outer whorl . . . . 32 ,, 



Locality. — Limerick (? near the city). 



Vestinautilus ckateeifok.mis, sp. nov. Plate XXIII, figs. 4 a — c. 



Shell thick-discoid, subglobose, transversely subquadrate in section, the 

 whorls all exposed in a deep, broadly crateriform umbilicus having a small central 

 vacuity. The margin of the umbilicus, which is very acute in the cast, was, 

 judging by a remnant of the test, apparently slightly keeled. The whorls overlap 

 to the edge of the umbilical margin of the preceding whorls, leaving only an 

 incised line to mark the place of this margin on the steep crater-like side of the 

 umbilicus. The umbilical slopes are somewhat inflated, as in V. cariniferus. The 

 peripheral area presents a low and broad arch which slopes a little more abruptly 

 near the umbilical margin ; faint traces of keels, one on each side of the latter, 

 are seen upon the well-preserved fragment of the test still remaining ; these keels 

 are perceptible also upon the cast. 



The body-chamber is imperfect, and is only a cast with fragments of the test 

 adhering. On separating it from the septate part of the shell the position of the 

 siphuncle is seen to be a little above the centre of the septum. The septa, the 

 sutures of which are clearly exposed on the cast, are somewhat shallow; the 



