22 



pearance, minute structure and habit, that it is eztraordinary that 

 any person should have made the proposal. 



I think the best way to show the distinetion of these two genera 

 will be to copy, in addition to the extract already given, the figures 

 (see figs. 1 and 2) and descriptions of the animals given in different 

 authors, commencing with Mr. Lowe, who has figured and deseribed 

 the animal of Truncatella in the fifth volume of the ' Zoological 

 Journal,' and Mr. Berkeley's description and figure of the animal of 

 Assiminia ; then the desciiption of the animal of the Indian species 

 of the latter genus, both printed in the volume above* referred to ; 

 and, lastly, some extracts of additional peculiarity of the genus 

 Truncatella, observed by Mr. Clark, and published in his work on 

 British Mollusca. 



" 1. Truncatella. R. T. Lowe, Zool. Journ. v. 299. 1. 19. f. 4. 



" Tentacula (2 contractilia) cyUndrico-conica, brevia, obtusa, basi 

 distincta, proboscide separata; oculis sessilibus paullo supra basis 

 ungulum externum positis. Caput proboscidiforme exsertum. Os 

 ad extremitalem proboscidis cylindricce, inter tentacula esserta, 

 disciformem, supra emarginatain (sc. bilobam, ob buccas labiales in 

 proboscidem ipsam coadunatas vel commutatas). Pallium collare 

 siphone nulio; orificio ad dextrum corporis ut in Helice, Melam- 

 pode, Pedij)ede, <^c. Pes rotundatus vel ovalis, brevis, minimus, 

 posticus. Operculum corneum simplex, i. e. non spirale, ovale, 

 aperturam testą omnino claudens'. Testą turrita; adulta cylin- 

 drica, decollata vel truncato-obtusa ; anfractibus distinctis, vel 

 Icevibus vel transverse costatis. Apertura ovalis, brevis; peri- 

 tremate cojitinuo. Labrum simplex. Epidermis nulla. 



Animal littorale, amphibium, sed revera marinum et branchiis 

 spirans. Ingredienti, discus terminalis proboscidis pro pedis parte 

 antica scrvit; itaque moda f ere larvarum Phalcenidarum Geome- 

 trarum gradibus alternis incedit. Testą junior, tereti-acuminata, 

 e pluribus anfractibus quam adulta constat; prioribus in plerisgue 

 demum {ut in Hel. Bulimo decollato) defractis, truncata cvadit. 



"Itisnownearly three years (1829) since the acąuisition of a single 

 live specimen of Cyclostoma truncatulum, Drap., and a long and 

 contmued observation of its animal, convinced me that it was eutitled 

 to rank as a distinct genus froni any which were then constituted. 

 I had accordingly designated it in my MSS. by the generie name of 

 Herpetometra ; derived from its peculiar manner of crawling. This 

 appellation I had since purposed changing into Truncatella, the very 

 name by vehich I fiud the self-sanie species designated by Risso in 

 his ' Histoire Nat. &c. de l'Europe Me'ridionale.' In this work, 

 however, the genus rests, likę very many others of the šame writer, 

 on most unsubstantial ground, the animal being entirely neglected." 



• "Assiminia. Berkeley, Zool. Journ. v. 429. t. 19. f. 4. 



" Voluta denticulata, Mont. {Carychium Myosotis, Michaud, 

 Compl. de r histoire de Drapard.), and Assiminia Grayana, Leach, 

 abound undcr stones in the salt marshes by the Thames at Gravesend. 



