Here are the top common species and counts at WB, as per Emerson's book.

1. Coral - Turbinolia pharetra 1000 (common, ranges from 5mm and up)
   
2. Bivalve - Anomia lisbonensis 1000 (fairly large)
   
3. Bivalve - Barbatia (Barbatia) uxorispalmeri 1000
   
4. Bivalve - Notocorbula texana 1000
   
5. Gastropod - Latirus moorei 1000
   
6. Gastropod - Polinices aratus 600 (very common snail, as a Naticid, drills holes in prey)
   
7. Bivalve - Vokesula smithvillensis petropolitana 500
   
8. Gastropod - Buccitriton texanum 500 (very common snail, and a predatory hole driller)
   
9. Gastropod - Hesperiturris nodocarinatus 500
   
10. Bivalve - Pachecoa (Pachecoa) sabinica 308
    
11. Gastropod - Buccitriton sagenum 300 (predatory snail drills holes)
    
12. Gastropod - Turritella nasuta 300 (oddly, a filter feeder)
    
13. Bryozoa - Lunelites bouei 253
    
14. Bryozoa - Schizorthosecos interstitia 253
    
15. Gastropod - Mesalia claibornensis 250
    
16. Gastropod - Protosurcula gabbii 250
    
17. Scaphopoda - Dentalium (Antalis) minutistriatum 244
    
18. Gastropod - Michela trabeatoides 240
    
19. Gastropod - Pseudoliva vetusta CONRAD FORMA 232
    
20. Bivalve - Vokesula smithvillensis smithvillensis 200
    
21. Gastropod - Bonellitia parilis 200
    

And with additional information added:

Emerson's book provides info on the number of specimens in his collection. The rarest species, of which there are many, are represented by only one specimen. The more common specimens range from a few to an unspecified, large number.

Most of the time, he provides an exact count. Example: 232. Often, he provides a minimum value, such as 250, meaning that there were at least 250 specimens in the collection. Other times, he omits a number, but states the species is very common. These latter specimens are noted above as the number 1000.