METAZOA MOLLUSCA. 225 



Murex (No. 478, M. tenuispina Lam.), is an illustration 

 of a specialized shell of this group. In this species the 

 protoconch is preserved as a tiny white pearly shell. 

 Extending below this are two or three whorls with ridges 

 but without the long slender projections which ornament 

 the succeeding whorls to an extreme degree. 



Conus bandanus Brug. (No. 479), is like an inverted 

 cone, the last whorl being large and making most of the 

 cone. The number of whorls can be indistinctly traced, 

 encircling the apex at the broad posterior end. The aper- 

 ture is neither notched nor drawn into a long canal. 



Trochus ( Tectus) fenestratus Gmel. (No. 480), is a 

 tightly coiled tube, the w^horls increasing in number and 

 being uniform in ornamentation. 



Aulica deshayesi Reeve (No. 481), is a'n instructive 

 species since the protoconch is so large that its distinctive 

 characters can be seen and thereby the ancestral form of 

 the genus determined. This embryonic shell is a plump, 

 globular spiral, light colored and smooth, and revolves in 

 a different plane from the rest of the shell. One can dis- 

 tinctly make out where the nepionic stage begins by not- 

 ing the origin of the revolving lines and vertical ridges. 

 The ephebic stage lasts until the ridges begin to dis- 

 appear, as seen in No. 481. The vertical markings 

 become coarser, which are characters of the gerontic 

 stage. Oliva erythrostoma Lam. (No. 482), is similar in 

 the different stages, as shown in the specimens, but by 

 examining the apex, a colorless translucent spiral is seen 

 which represents the ancestral form. The last whorl con- 

 stitutes most of the visible shell, but the number of whorls 

 encircling the apex can be easily counted. The specimens 

 show considerable variation in color. 



The resemblance of Oliva, Aulica, and the like to the 

 young Cypraea argues for a close relationship between 

 these forms. 



In Cymbium cymbium Linn. (No. 483) , the apex is 

 smooth and flattened, and only two whorls are visible. 



