374 



]\lr. E. A. Sinitli 0)i tJie Genera 



to add that the iiiickus is central, and, in character, tlie 

 operculum is similar to that of lurrittlla, which is also 

 multispiral, and not ]\aucispiral, like tliat of MiSalia. Tlie 

 gemus will include Turiltella ?v'//e»Za/a, Mighels & Adams, 

 2\ et-osn, Couthouy, 7'. enchrichiii, Middendorff, Mesalia 

 lacteola, Carpenter. 



All of these species have an arctic appearance, being 

 chalky white, and clothed with a thin yellowish-olivaceous 

 periostracum, differing in this respect from Tui-ritella, which 

 exhibits scarcely any traces of it, or might even be described 

 as devoid of it. 



The radulfe of T. reticulata and T. erosa are of the same 

 characttr as that of Tia-ri'tella, and the differences noticeable 

 are ])robably merely specific. 



The base of the aperture in Tachyrhynchus exhibits more 

 or less of a sinus, it being most distinctly shown in 2\ lacteola, 

 Cpr. In Turritella there is no such euiargination oreffYision. 



Tachyrhynchus is at once separable from Mesalia by the 

 different operculum, and its boreal ciiaracter. Like Turri- 

 tella, Mesalia exhibits usually only very faint indications of 

 tiie periostracum. 



Tachyrhynchus erosa (Couthouy), 



1838. Turritella erosa, Couthouy, Boston Journ. Nat. Ilist. vol. ii. 



p. 10.3, pi. iii. ii;^. 1. 

 1S41. Turritella erosa -. Gould, Invert. Massachii.<!ett.<>, p. iiG7. 

 1842. Turritella pularis (Beck MSS.), MiJller, ludex Moll. Greenland. 



p. 10. 

 It'-lO. Turritella erosa : Middendorff, Malac. Koss. p. 68. 

 18.52. Turritella erosa : Mcirch, Cat. Conch. Yoldi, p. 54. 

 1857. Turritella erosa : Mcirch, Rink's Gronland, vol. ii., Naturhist. 



Bidra^S p. 82. 

 1868. Tuvhijrijnchus erosa : ^MiJrch, Amer. Journ. Conch, vol. iv. p. 46, 



animal. 



1870. Turritella erosa: Gould, Invert, Massachusetts, ed. 2, p. 317, 

 fig. 585. 



1871. Mesalia polaris: Dall, Amer. Journ. Conch, vol. vii. p. 118. 

 1877. 'Turritella erosa : Jeilieya, Ann. & Mag. Nat. Hist. vol. xix. 



p. 239. 

 18c5o. Turritella erosa: Aurivillius, Vega-E.xped. vol. iv. p. 322, pi. xii. 



fig. 7, pi. xiii. fig. 17 (radula), 

 1886. Turritella (Turritellopais) erosa: Trvon, Man. Conch, vol. viii. 



p. 208. 



Hah. Massachusetts {Couthouy S,- Gould) ; ]\laine {Blaney); 

 Labrador (Bush) ; Greenland [MoHer) ; Davis {Straits 

 (' Valorous'' Exped.) ; Nova Scotia {Brit. Mus.). 



The operculum of this species is described by Morch as 

 similar to that of reticulata, and a specimen in the British 

 Museum confirms his description : '' Horny, yellow, orbicular, 



