589 



The following are the plants included in the latter of the two 

 classes, and the principal points noticed with regard to them. 



1 . Sphceria angulaia, Fr. The occurrence of a state of fructifica- 

 tion similar to that in the genus Cryptosporium ; the varieties of 

 structure in the normal sporidia, and the probable origin and nature 

 of the abnormal fruit. 



2. Sphferia lanciformis, Fr., and Hendersonia polycystis, B. & Br. 

 Irregularity of form in the sporidia of Sphceria lanciformis. The 

 growth of perithecia in the same stroma, some producing the fruit of 

 Sphceria lanciformis, others that of Hendersonia polycystis. Notice 

 of the probable existence of a third form of fruit of Sphceria lanci- 

 formis. 



3. Sphceria siparia, B. & Br., and Prosthemium betulinum, Kunze. 

 Constant association of the two forms ; their external resemblance ; 

 nature of the fruit and other circumstances leading to the conclusion 

 of the identity of the two plants. 



COMMUNICATIONS RECEIVED SINCE THE END or THE SESSION. 



I. "On the Anatomy of Tridacna" By JOHN DENIS MAC- 

 DONALD, Esq., Assistant- Surgeon R.N. Communicated 

 by Sir JOHN LIDDELL, C.B., M.D., Director-General of the 

 Medical Department of the Navy. Received June 25, 

 1857. 



(Abstract.) 



The author first explains the peculiar position which the animal 

 of Tridacna occupies in its shell, in which it differs from bivalves in 

 general. He then describes the mantle and its borders, the mem- 

 branous interpallial septum, the respiratory and wide pedal openings 

 communicating with the interpallial space, the two pairs of branchiae, 

 the mouth with the anterior and posterior lip and the four oral 

 palps, the foot, the extensive cloacal cavity with its subdivisions, and 

 the circular contractile cloacal orifice opening on the dorsal surface. 

 He next gives an account of the form and arrangement of the ali- 



2 u 2 



