Soine new Upper Ch'eensand Gasteropods. 287 



very oblique, those above very slightly so. Umbilicus not small. 

 Mouth angular above, twice as wide as high, half the width 

 of the shell. The whorls being convex, there is a hollow 

 round the suture, which in the last whorl gradually becomes 

 effaced, pi'oducing a flat upper surface, nearly horizontal. The 

 outer convex part of the upper whorl also becomes flat and 

 oblique, and is much wider than the inner part. The ribs are 

 on the angle between these areas of the shell. The base be- 

 comes more gently round ; and in the cast the tubercles are 

 obliterated on the last half- whorl. With age the shell thick- 

 ened ; so that in the cast the markings are only visible on the 

 last whorl. 



A specimen in the University Museum, collected by Mr. 

 Archer (Trin. Coll.), measures 1| inch across. This fine species 

 (the largest our bed has produced) is distinguished rather by its 

 combining the characters of other forms than by anything pe- 

 culiar. It has the inflated shell and tubercles of S. cirruide and 

 the angular margin of S. dentatum. 



Very rare. University Museum. 



Solarium planum. PI. XI. fig. 11. 



Shell discoidal, composed of about six whorls, which are flat on 

 the upper side, and separated by a deep suture. Under side 

 slightly hollow ; all the whorls exposed and separated by a 

 suture. The outer edge of the dorsal surface has a row of 

 prominent tubercles, about twenty-seven on a whorl. On the 

 inner edge of the whorl, bordering the suture, is a row of less 

 prominent tubercles, about thirty on a whorl. From the 

 spaces between the tubercles extend on to the whorl little 

 furrows which make its surface undulating. Between the 

 rows of tubercles are five little ribs. The side of the whorl is 

 also marked with strire, and has in the middle a prominent 

 keel, which is granulated. The outer edge of the base is 

 marked with a row of tubercles more" prominent than that of 

 the top, about twenty on a whorl ; on the inner edge above 

 the suture is a row of more than forty small granules, from 

 which branch out numerous little plicae. Outside of the 

 mouth pentagonal ; inside round. Diameter rather less than 

 ^ inch. 



The cast is round. 4. 



This elegant species is most nearly related to S. Martinianum 

 (D'Orb.), but differs in the pentagonal mouth, plain ungranu- 

 lated ribs, keel, &c. 



Specimens in the cabinet of Mr. Carter exhibit external casts 

 of the entire shell. Very rare. 



