24 MOLLUSCA FROM THE CRAG. 



with its superior extremity extended in the form of an elongated and very narrow 

 canal ; base with sometimes a lengthened siphonal canal, and a sinus in the lower 

 part of the outer lip. 



Rostellaria plurimacosta. S. Wood. Catalogue of Crag Shells, 1842. 

 A few worn specimens of a species of Rostellaria are in my cabinet, from the Red 

 Crag of Sutton. They are in a mutilated condition, and unfit for fair comparison ; 

 they bear a resemblance, and may possibly be the B. lucida, J. Sow. (Min. Con. t. 7), 

 perhaps washed out of the London clay. 



Aporehais,* Aldrovandus. 



Rostellaria. Lam. 1801. 

 Chenopus. Phil. 1836. 



Gen. Char. Shell turreted or fusiform, thick and strong, generally ribbed, nodu- 

 lous, or carinated ; aperture ovate or elongate, terminating in a canal with a cal- 

 careous pointed process at the base, and having, in the adult state, an expanded 

 angularly lobed, or digitated outer lip, sinuated at the lower part near the canal. 

 Operculum corneous. 



The name for this genus was used by Aldrovandus in 1623, and by Petiver in 

 1702, when describing the pes-pelicani with the following words : " Aporrhais Edin- 

 burgensis minor nodosa." (Grazophylacium, fol. 17, Tab. 79, f. 6, and Tab. 127, f. 

 11, Cat. No. 85.) Da Costa (History of British Shells, 4to, 1778) characterizes the 

 same species under the name of Aporrhais with a new specific appellation, and a refer- 

 ence to Petiver. In the ' Philosophical Transactions ' for 1823, Dillwyn uses the same 

 name as a generic term, and applies it to the pes-pelicani ; and this may be considered 

 as a fair revival of a name proposed before the time of Linna?us. This species, upon 

 which the genus has been established, was included by Lamarck in Rostellaria, in 

 consequence of the sinus in the lower part of the outer lip resembling the shells of 

 that genus. 



In 1836, M. Philippi (Enum. Moll. Sic. vol. i, p. 215) described the animal of 

 pes-pelicani, which, he says, is decidedly different from that of Rostellaria, and 

 proposes, in consequence, to erect it into a genus, under the new name Chsnopus, 

 with the pes-pelicani as its type. 



It has been contended that the genus was in the first instance established upon 

 the form of the shell alone, without a knowledge of its animal inhabitant ; and tbat a 

 detection of a difference in some of the soft parts, with a publication of the anato- 

 mical details, will justify the rejection of an old established name and the substitu- 

 tion of a new one. A principle which, if admitted, will endanger the stability of 

 many other genera that have been formed upon the shell alone, and priority of date, 

 as now considered, will be no security for an author's name. 



* Probably derived from airopf)a£ or aimppu)^, rent, torn, in allusion to the ragged or digitiform 

 processes of the outer lip. 



