northumberla>;d and dukiiam. 279 



The form which was separated under the epithet L. Tunstall- 

 ensi's ill the " Tyneside Catalogue," and in the " Cat. Org. Rem." 

 under the specific name Turbo Thomsonianus^ must also be referred 

 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 stride are finer and closer to 

 each other, and do not affect the rotundity of the whorls, as in 

 typical individuals. The Rissoa Gibsoni, Brown, ajDpears to be 

 only a cast of this variety, which is also described by Geinitz as 

 Trochus pusillus, Verst. pi. 3, f. 15, IG. 



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

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

 stride are more numerous, more closely set, and thicker in appear- 

 ance than usual. 



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

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

 ?nmuta, Brov/n. 



In the first variety may be placed Rissoa obtusa, Brown, Natica 

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

 variety, Rissoa Gibsoni, Brown, Trochus pusillus, Geinitz, Litto- 

 rina TunstaUensis, Howse, and Turbo Thomsonianus, King. 



Note on .the originals of Capt. Browns species. — Turbo Man- 

 cumensis. Mr. Binney's three oi'iginal 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 nmch rubbed. The other two 

 had the marking 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 one-fourth of an inch in length. It has three strong ribs on the 

 body-whorl, with an intermediate faint one above, and several 

 smaller, closer stride 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 (>f 

 T. Mancuniensis, as is well shown by the unfinished state of the 

 mouth of one of the specimens. 



