46 



TROCHUS. 



form (fg. 37), with a quadrangular aperture, and an extremely 

 flaring umbilicus (Jig, 38, u) ; the anterior edges of all the invo- 



Fig. 39. TROCHUS AGGLUTINANS. 



Fig. 37. SOLARIUM PfiRSPECTIVUM. Fig. 38. 



lutions or whorls of the spire are marked by a crenulated cord, 



that is, notched on the edge (Jig. 38). 



30. Among the TROCHI 

 properly so called, with an 

 umbilicated shell, we will men- 

 tion the Trochus agglutinans y 

 which is found in the West 

 Indies and Pacific. It has the 

 singular faculty of glueing to 

 itself movable bodies found on 

 the ground on which it rests ; 

 sometimes it glues stones and 

 sometimes shells or pieces of 

 shells, according to the place 

 where it is found. From this 

 habit of building out its habita- 

 tion from materials not its own, 

 it is sometimes called the Ma- 

 son (Fig. 39). 



There are some without an 

 umbilicus, very conical, and 

 very tall, that are marked by 

 numerous whorls in the spire, 

 with crossing striae ; the ex- 

 tremity of the columella is 

 much twisted, and projects be- 

 yond the origin of the lip. A 

 specimen of this variety is seen 

 in the annexed figure of the 

 telescope trochus (Fig. 40). 



Fig. 40. TROCHUS TELESCOPIUM. 



30. What are the peculiarities of the Trochus Agglutinans ? 



