Descriptions of Four New Species of Terrestrial Shells. 157 



XXIII. — Descriptions of Four New Species of Terrestrial Shells, 

 from Siam. 



By Wm. A. Haines. Read October 22, 1855. 



1. Cyclostoma Housei. 



Plate V. Figs. 12-15. 



T. latissime umbilicata, discoidea, solida, striatula, strigis crebris angu- 

 latis castaneis picta ; spira parnra elevata ; sutura canaliculate ; anfr. 5 

 convexiusculis, ultimo antice valde soluto, descendente ; apertura circu- 

 lar! ; perist. incrassato in tubulo retrorso extenso. 



Operc. extus convexum, lamellis angustis 3-4 spiratis convolutum, 

 intus concavcim, uitidum. 



Diam. maj. 26, min. 21, Alt. 13 mill. Ap. 10 mill. diam. 



Habitat. — Siam. 



A very remarkable species, belonging to the subgenus 

 Pterocyclos. The last whorl is much separated from the others, 

 and is furnished with a 'remarkable tube close to the aperture. 



I take great pleasure in dedicating this species to my friend, 

 Dr. Samuel K. House, to whom I am indebted for this, as well 

 as many other new and interesting Siamese shells. 



2. Cyclostoma Myersii. 



Plate V. Figs. 9-11. 



T. perforata, ovato-oblonga pupaeformi, latere apertura? compresso, 

 opposito inflato ; solida, sublaevigata, castanea ; spira oblongo-conica • 

 apice obtusa ; anfr. 6 convexis, ultimo attenuate, penultimo pone com- 

 presso ; apertura subverticali, subcirculari, snpertie angulata ; perist. 

 continuo, incrassato, expanso, subreflexo, flavo. 



Operc. ? 



Long. 36, diam. 18 mill. Ap. intus 10 mill, longa. 



Habitat — Siam. 



This species belongs to the subgenus Megaloinastoma, and is 

 the largest of this division of the genus which I have vet 

 observed. 



