1. 
   Palaeoheterodonta
   (from the article `bivalve`) ...often lost in adult; scallops capable of swimming; some deepwater scallops predatory; marine; epibyssate; cemented by lower or left valve or ... ...of subhabitats, with simple reproductive strategies, external fertilization, and planktonic larvae to effect wide disper...
   Found op http://www.britannica.com/eb/a-z/p/6
   
   
2. 
   Palaeoheterodonta
   Palaeoheterodonta is a subclass of bivalve molluscs. It contains the extant orders Unionoida (freshwater mussels) and Trigonioida. They are distinguished by having the two halves of the shell be of equal size and shape, but by having the hinge teeth be in a single row, rather than separated into tw...
   Found op http://en.wikipedia.org/wiki/Palaeoheterodonta
   
   

Tip: double click on a word to show its meaning.