NOTES ON THE CAMBRIDGE GREENLAND* 493
possessing three rows of tubercles instead of four, yet there are many characters common to the two species ; and it must be remem- bered that tubercles are sometimes represented by ribs as in T. eostatus.
Altogether I consider that the above-mentioned species hold such relations to one another as make it only reasonable to suppose that they have been produced by descent with modification.
The Cambridge form might receive the name of T. canta- brigiensis*
? Turrilites Emericianus, D'Orb.
Turrilites Emericianus, D'Orb. Pal. Pr. pi. cxli. figs 3-5.
The Woodwardian Museum possesses a small dextral cast, which appears to be referable to the above species, or is, at any rate, very closely allied to it.
Only two whorls are preserved ; but these are sufficient to show its low squat growth, and to distinguish it from T. Hugardianus. These whorls are rounded and ornamented with about 24 simple straight ribs, running down into the umbilicus, which is wide and ample.
Turrilites elegans, D'Orb.
This species does not yield a very well-marked cast; several specimens, however, have passed through my hands which greatly resembled it ; one of these is now in the Museum at Jermyn Street.
Turrilites nobilis, new sp. PL XXI. fig. 1.
Cast rather large, dextral, whorls full and rounded, crossed some- what obliquely by 26 to 28 well-marked ribs, each bearing three small tubercles ; the lower row of these is only seen on the body- whorl, being sutural in the whorls above. The ribs appear to run under the base, and to converge towards the umbilicus, their impressions being seen on the broken uppermost whorl.
The spiral angle is very small ; and the whorls were probably nume- rous, as in T. Hugardianus, from which it is easily distinguished by the rows of tubercles. The specimen above described was collected during the progress of the Geological Survey ; and the last whorl of a cast apparently belonging to the same form is preserved in the Woodwardian Museum. The actual shell is unknown, but was probably thin, as in other Turrilites ; so that its characters are suffi- ciently delineated by the cast : I have therefore thought that the species might safely be described and named. From T. Wiestii it is distinguished by the broader whorls and less prominent tubercles, in this respect approaching T. Escherianus,
