526 Forty-fifth Report on the State Museum. 



The species in which the lower surface of the brachia is attached 



Fig. 178. — Megathyris decollata. n., 

 foramen; o, deltidial plates; g, crura; 

 I, lobed extension of brachial supports- Fig. 179. — Cistella neapoli 



<Bronn.) tana. Interior of brachia- 



valve. (Woodward.) 



to the mantle, have a sim- 

 ple vertical lamella (Cis- 

 tella), which may be 

 lobed (Megathyris, Bac- 



TRYNIUM, EuDESELLA,DaV- 



idsonella, etc.). In The- 

 cidium,Thecidella,Laca- 

 zella, etc., the defini- 

 tion of the lamella is ob- 



Fig. 180.— Interior of brachial and pedicle valves of The SCUred, the Spicular net- 

 cidium radiafoim. o', deltidium; fcfc', teeth; ab, adductors; i bpino* loo^P and 



e', diductors; 7i, cardinal process; 

 brachial supports. (Suess.) 



cardinal plate; g, 



sponge-like. The brachio- 

 pods which were not possessed of elaborate brachial supports may 

 have long calcareous crura, as in Rhynchonella and its allies, or 

 even these may be wanting, as in Strophomena, Plectambonites and 



Productus. Such shells, 

 however, sometimes retain 

 grooved impressions made 

 by the spiral arms upon the 

 inner surface of the valves 

 (Davidsonia,Kafinesquina) 

 InCHONETES and Productus 

 there are two divergent 

 impressions on the brachial 

 valve, which are commonly 

 known as the reniform 



Fia. 181. — The interior of the pedicle- valve of Ka fi n - f/i(X^ki?lOS and these are 

 esquina Jukesi, showing the impression of the spiral " ' 



arms. (Davidson.) generally regarded as due 



to the brachia, though their precise relation to these organs has 

 not been satisfactorily explained. 



T8 



