MISS DONALD : ON TCREITELLID.E AND MUKCEISONIID.E. 49 



Certain species referred to the section Haustator, Montf., instead of 

 having the outer lip merely sinuated as in the type, have a broad 

 shallow sinus, viz., Turritella rosea, Quoy, T. cingulata, Sby., and 

 T. cingulifera, Sby. T. austral is, Lam., has also a broad shallow simis 

 in the outer lip, and lias been referred by Kobelt, with a query, to 

 Zaria, Gray, but the form of the aperture in that section is different, 

 and the species agrees more in character with those just mentioned. 



These shells with a broad shallow sinus are evidently closely 

 related to the type of Turritella, and are quite distinct from those 

 with a deep sinus ; but it remains to be decided in what degree the 

 latter are related to the genus. This can only be ascertained by 

 a minute and detailed examination of the animals. Similar investi- 

 gation of the animals of the types of Turritella, and the various sections 

 referred to that genus, is also necessary, in order that it may be 

 ascertained whether any special structural features are associated with 

 the differences in the form of the aperture. Hitherto these detailed 

 comparisons do not appear to have been made. Data will thus be 

 furnished for determining the affinities of fossil shells having analogous 

 forms. 



Elongated Gastropoda having a sinus, or slit, in the outer lip occur at 

 a very early epoch, being abundant in the Palaeozoic Period in company 

 with the shorter Pleurotoniariae. Unlike these latter, however, which 

 reached their maximum in the Jurassic Period, and continue up to the 

 present time, being now represented by five species, Murchisonia and 

 its associated forms became almost, if not entirely, extinct after the 

 Triassic Period. The only shells which at all resemble them are 

 Disoketa Meyeri, Gardner, from the Gault, which possesses two 

 channels bordered by slightly elevated keels, and the genus Murchi- 

 sonella, Morch, species of which occur in the Eocene beds near Paris, 

 and living at the Island of St. Thomas, West Indies. This last genus 

 is referred to the Turbonillidaa, because the protoconch is heterostrophe. 



Special interest therefore attaches to these recent shells with a deep 

 sinus, and it is to be hoped that some light will soon be thrown on 

 the structure of the animals, as in the recent Pleurotomariida). The 

 studies of Dall, Pischer, Bouvier, and others show, as might be 

 expected, that the anatorny of these latter is of a primitive type. 



The number of recent shells with a deep sinus in the outer lip 

 that have been described up to the present is seven, viz. : Turritella 

 aeeisa, Watson, T. runcinata, Watson, T. deliciosa, Watson, T. cordismei, 

 Watson, 1 T. sinuata, Reeve, 2 T Soph ice, Brazier, 3 and T. Higginsi, 

 Petterd. 4 



There are three specimens of T. aeeisa in the British Museum 

 (Natural History) dredged by the "Challenger" off East Moncceur 

 Island in 38-4U fins., and also three other examples which are 



1 "Challenger" Reports, Zoology, vol. xv (1886), pp. 469, 471, 475, 476. 



2 Conch. Icon., vol. v (1849), pi. xi, fi£. 62. 



3 Proc. Linn. Soc. New South Wales, vol. via (1883), p. 227 ; vol. ii (1877), p. 262. 



4 Journ. Conch., vol. iv (1884), p. 13-5. 



