UNIVALVES. 



PLATE X. 



Genus. DISTORTA. 

 Character. Shell spiral, each revolution of the spire unequally placed, and gib- 

 bous, or bellying out ; mouth resembling a cavern, and, together with the maxilla 

 oris, carunculated all over, and armed with numerous teeth on each side. Only 

 two species are at present known, which are the following : 



No. 1. Distorta acuta. Shell yellow, and covered with hollow reticulations, 

 similar to net- work ; mouth brown, having a curious flap expanded on each 

 side. A native of New South Wales. 



No. 2. Distorta rotunda. Shell red, with a white mouth ; inside brown ; the 

 mouth invested with a curious flap, which is scutellated, or edged like an 

 ancient shield ; the spire, like the other, equally irregular in its form. A 

 native of the Southern Ocean. 



Genus. ROSTELLARIA. 



Character. Shell spindle-shaped, or sub-turreted, ending at the base in a canal, 

 stretched out like a sharp beak; cheek joined to the spire; lip whole, or denticu- 

 lated, increasing by age ; a lacuna near to the canal. 



Species. 

 No. 1. Rostellaria sinensis. Shell spiral, and variegated with red and yellow; 



mouth contracted, and placed under the body. This shell is found in the 



Chinese Seas, and sometimes attains to a large size. 

 No. 2. Rostellaria pes-pelicani. Shell turreted and spiral ; the lip spread out 



like a sail, and divided into three points ; the back of it resembling the foot 



of the white Pelican. It is a native of the British Seas, and the Hebrides, 



or Western Isles. 

 No. 3. Rostellaria dentula. Shell red ; the channel at the top of the mouth 



very large and obvious ; the cheek furrowed at the edge into five or six 



teeth. This curious and rare shell is a native of the East Indies. From 



the original in Dr. Combe's Museum. 



REMARKS. 



The genus Distorta is remarkable in its form, and so unlike any other at present known, as 

 fully to justify the placing it apart from all others. The inequality of the spire is its prin- 

 cipal characteristic, next to which is its singular mouth and lip, of a form different from all 

 other known shells. The genus Rostellaria bears a distant analogy to it, as does the genus 

 Septa, in respect to the spire. I have adopted the idea of Lamarck, in removing the genus 

 Rostellaria, from its original parent, Strombus, as indeed it would not range conveniently 

 either with the Murex or Buccinum. A very large fossil shell of this genus has been de- 

 scribed in the Branderian Collection of Hampshire Fossils, and is supposed, when perfect, 

 to have a good deal resembled in its form No. 2 of the present Plate. The science of fossil 

 shells seems calculated to throw an additional light upon the distinctions of the genera, 

 though, in form, they never appear exactly to imitate any of the recent living specimens. This 

 question however is still open to the investigation of the Naturalist, as more specimens may 

 in future be discovered. 



