ROSTELLARIA. 



Genus ROSTELLAEIA, Lamarck. 

 Testa ftmfoi'mis, baai in canalem interdum gracilUmmn et 

 eloiigcdnm desitiens, spird valde acnminatd, anfradibus 

 nunc laviius, mine costatis aut sulcatis, labro miiri- 

 cato-dentato, superne canaliciilato-producto, interdum 

 expanso et dujitato. Opercidum corneum, ollongum, 

 atigitstum, 7nedio cosiatim. 

 Shell fusiform, ending at the base in a canal, which is 

 sometimes very long and slender, spire very much 

 acuminated, whorls now smooth, now ribbed or 

 grooved, lip prickly-dentate, canalicidately produced 

 at the upper part, sometimes expanded and digitated. 

 Operculum horny, oblong, nan-ow, ribbed down the 

 middle. 

 The genus Rosiellaria, which is here adopted provisio- 

 nally in its Lamarckian fomi, under an impression that the 

 species which have been detached from it are not yet satis- 

 factorily understood, comprises three distinct gi-oups. The 

 first, which may be regarded as the type of the genus, in- 

 cludes B. curvirodris, curia, fusus, and Povisii. The shells 

 are large and fusiform, with little sculpture, and have the 

 lip conspicuously prickly dentated, and produced more or 

 less over the penultimate whorl into a channel. The 

 second fonn is represented by two species, E. cancellata and 

 crispata, of very much smaller dimensions, in which the 

 shell is of a different substance, and elaborately sculptured 

 like the small Tritons. In these the lip is not dentated ; 

 it still rises up into a canal, after the manner of the typical 

 RosteUaritt, extending in one of the species nearly to the 

 apex. The third form included under Rostellaria by 

 Lamarck, comprises those species which have been sepa- 

 rated by comnron consent, on account of a difference in 

 the animal, under the title oi Jporrhais. These are R.pes- 

 pelecaui, pes-carbonis, and occidentalis. In the first two 

 species the lip is expanded into very prominent claws, in 

 the last it is \videly expanded but not clawed. 



Professor E. Forbes proposes to associate the genus 

 Aporrhais along with Cerithium, in a family, Ceritldadci', 

 o\ving to certain corresponding features of the animal. 

 This family he describes as being closely allied on the 

 one hand to the TurritelUda, and on the other to the 

 Scalariadff . It is not intended here to differ from so high 

 an authority on living raoUusca, not having adequate data 

 for so doing, but it may be stated that all the observations 

 derivable from the form, growth, and substance of the 

 shells point to ;■- different ronelusiou. The relationship 



March 



between Aporrhais and Cerithium he derives from a simi- 

 larity between the aiumals, but it is veiy difficult to under- 

 stand how two genera, whose shells in all the species are 

 of so uniform and distinct a type, can be constructed by 

 a similar animal. It is a remarkable feature in the shell 

 of Aporrhais and of the family Alatu, that a sudden de- 

 parture from the spiral plan of convolution is given to 

 the shell on arriving at maturity. This is not so in Ceri- 

 thitmi, nor in any other genus of moUusks. Professor Forbes 

 remarks that " the affinities of Aporrhais and Cerithiimi 

 are very evident when we look at the young shells of the 

 former." The same may be said oi Strombits arxA. Conns. 

 The shells of many genera, far removed from each other, 

 agree in their plan of convolution up to a certain age, yet 

 differ widely before reaching maturity. The relationship 

 between Aporrhais and the Scalariadre is said to be better 

 traced in fossO than in living examples. In having re- 

 course to the shell for this affinity, it should be borne in 

 mind that the adult shell of Scalaria, throughout a 

 hundred species, is of the simplest tubular form, and 

 what is prbably of more importance in reference to the 

 animal, of a peculiar semi-transparent substance, mostly 

 colourless. So far as regards the shell, Scalaria is pecu- 

 liarly distinct in all respects from Aporrhais. 



The typical species of Rostellaria inhabit the E.ed and 

 China Seas, the second group is from the Philippine 

 Islands, and the third inhabits the coasts of Em-ope and 

 Newfoundland. 



Species 1. (Mus. Cuming.) 



EosTELLAElA PES-CAKBONis. Rost. testd fusijormi, spird 

 acuminato-turritd, anfractibus tramversini undique 

 conspicue minute striatic, medio tumidis et eximie obli- 

 que plicatis, anfractu idtimo bi-tricarinato, carinis 

 minuti plicato-uodatis, in alum acute quinquedactylam 

 late expanso; semipellucido-albd, fuscescente partim 

 tinctd. 



The cormouant's foot Rostellaria. Shell fusiform, 

 spire acuminately turreteil, whorls transversely con- 

 spicuously minutely striated throughout, swollen and 

 delicately obUquely plicated round the middle, last 

 whorl two- tlu'ce-keeled, the keels being minutely pb- 

 cately nodided, broadly expanded into a sharp five- 

 clawed wing ■ semi-traiispareut white, partially tinged 

 with light l)rown. 

 1831. 



