Counties of Durhain and Northumberland. 469 



ensis in the Tyneside Catalogue, and in the ' Cat. Org. Rem.' 

 under the specific name Turbo Thonnsonianus, must also be re- 

 ferred to the L. helicina. It is smaller than the typical form of 

 helicina, and the spire is considerably drawn out, which gives 

 the whorls a much rounder appearance, and the striae are finer 

 and closer to each other, and do not affect the rotundity of the 

 whorls, as in typical individuals. The Rissoa Gibsoni, Brown, 

 appears to be only a cast of this variety, which is also described 

 by Geinitz as Trockus pusillus, Verst. pi. 3. f. 15, 16. 



King's T. Taylorianus is, I think, a very stunted form of this 

 species. It has the spire only very slightly elevated, and the 

 striae are more numerous, more closely set and thicker in ap- 

 pearance than usual. 



To the typical form of this species, Trochilites helicina, Schloth.^ 

 may be added the Turbo Mancuniensis, Brown, and the Turbo 

 minuta, Brown. 



In the first variety may be placed Rissoa obtusa. Brown, Na- 

 tica minima, Brown, and Turbo Permianus, King ; and in the 

 second variety, Rissoa Gibsoni, Brown, Trochus pusillus, Gei- 

 nitz, Littorina Tunstallensis, Howse, and Turbo Thomsonianus, 

 King. 



Note on the originals of Capt. Brown's species. — Turbo Man- 

 cuniensis, Mr. Binney's three original specimens of this shell, 

 from the Permian marls of Lancashire, are rather more obtuse 

 in the spire than those from the shell-limestone of this district. 

 The whorls have also a more rounded appearance. One of the 

 specimens was worn, and very much rubbed. The other two 

 had the markings sharp and well defined. Aperture nearly cir- 

 cular, with a slight notch behind the pillar-lip, but no umbilicus. 

 The largest specimen, which shows the mouth, not quite perfect, 

 is I of an inch in length. It has three strong ribs on the body- 

 whorl, with an intermediate faint one above, and several smaller, 

 closer striae beneath. The two specimens of Turbo minutus in 

 the same collection are undoubtedly, as I pointed out formerly 

 in the Tyneside Catalogue, only the younger state of T. Man- 

 cuniensis, as is well shown by the unfinished state of the mouth 

 of one of the specimens. 



Two of the original casts of Rissoa obtusa. Brown, are not in 

 a state good enough to describe. One of them is very much 

 compressed. The other specimen is more perfect than these, 

 but is also a cast. It has four rounded whorls and a short 

 spire, but the apex is not quite perfect. The Natica minima. 

 Brown, a cast with imperfect spire, is undoubtedly the same as 

 R. obtusa. The originals of Capt. Brown's Rissoa Gibsoni are 

 also casts. Two of them are very much compressed, so that 

 the spire has not the natural appearance. The third speci- 



