1871.] 



151 



[Morse. 



Fig. 1. 



Fig. 2. 



made by Forbes and Hanley in their standard work on the Brit- 

 ish Mollusca, wherein the shelly plug which escapes through the 

 sinus of the flat valve to hold the 

 animal to its base of attachment 

 is compared to a byssus. They 

 say "when the very young fry of 

 this genus shall have been care- 

 fully observed, we believe they 

 will be found spinning a byssus, 

 which, passing through this sinus, 

 fixes the shell in the first instance, -pig. 3. 

 before a portion of it becomes 

 attached, eventually becomes de- 

 tached with a part of the "adduc- 

 tor muscle, and forms the opercu- 

 lar process." 1 



They erred only in conceiving 

 that the byssus passed through a 

 sinus occupying the same position 

 as in the adult; this is not so, as Flg ' *■ 

 will be shown presently. 



Lacaze Duthier, after his ex- 

 haustive study of the organiza- 

 tion of Anomia, refers to these 



Fig. 1. flight or lower valve of 

 Anomia, showing notch in ventral pal- 

 lial margin, caused by byssus. Diame- 

 ter one sixty-fourth inch. Fig. 5. 



Fig. 2. Left or upper valve of Fig. 1. 

 Diameter one sixty-fourth inch. 



Fig. 3. Foramen commencing to 

 form. The black portion shows pro- 

 portions of left valve. 



Fig. 4. A more advanced stage of 

 right valve with foramen almost com- 

 pleted. 



Fig. 5. Left or upper valve of Fig. 4. 

 Diameter one thirty -second of an inch. Fig. 6. 



Fig. 6. Showing later stage, with 

 foramen completed, and nucleus still 

 visible. 



1 Forbes and Hanley, British Mollusca, Vol. II, p. 323. 



