40 



TROCHUS. 



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

 flaring umbilicus (fg. 38, u) ; the anterior edges of all the invo 



Fig. 39. TROCHUS AGGLUTINANS. 



u 



Fig. 37. SOLARIUM PERSPECTIVUM. Fig. 38. 



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



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



30. Among the TROCHI 

 properly so called, with an 

 umbilicated shell, we will men- 

 tion the Trochus agglutinans, 

 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 ? 



