CHAPTER LIV: THE SLIT SHELLS 

 Family Pleurotomariid^ 



Shell top-shaped, pearly within, with a broad anal sinus 

 in the outer whorl which closes gradually, forming the "sinus 

 band." A family of many fossil forms allied to Haliotidae. 



Genus PLEUROTOMARIA, Defr. 



Characters of the family. Eleven hundred fossil species 

 of this genus are known. The recent discovery of living forms 

 corrects the old opinion that the genus is totally extinct. Twenty 

 good specimens have been collected in the past fifty years. They 

 are large, and so distinct in kind as to be in great demand among 

 collectors. The single specimen of P. Quoyana, F. and B., was 

 purchased by an amateur in 1873 for 25 guineas. A fme large 

 P. Adansoniana, Cr. and Fisch., is priced at ;£ioo sterling. 

 Both of these species have been found in the region of the 

 West Indies. The American Museum of Natural History has a 

 three-inch specimen of P. Beyrichi, Hilgendorf, which was 

 dredged in deep water off the coast of Japan. It is decorated 

 with yellow and red in fme streaks on its top-shaped spire, and 

 the sinus band ends in a deep slit at the upper (sutural) edge of 

 the lip. The largest Adansoniana, taken alive from water one 

 hundred fathoms deep off Guadaloupe, measured more than 

 five inches across. 



The Little Slit Shells (genus Scissurella) are very small, 

 thin-shelled mollusks with the tell-tale slit in the shell's lip. 



221 



