496 



Forty-fifth Report on the State Museum. 



of the valves so strongly that their traces are visible when the 

 shell is petrified, and may be seen not only over the brachial 

 region but also where the mantle is extended posteriorly between 

 the margins of the visceral area and the edges of the valves 

 the parietal region). 



Fig. 101.— Marginal portion of the mantle of Fig. 102.— Vertical section of shell and mantle of 



Magellania australis. 

 a, margin; b, marginal fold; c, setae; d, 

 follicles of setae; e, circumpallial muscu- 

 lar belt; g, pallial muscles; h, bases of 

 pallial caeca.— (Hancock). 



Magellania a ustralis. 

 a, margin of valve; 6, shell showing prismatic 

 structure; c, pallial cseca penetrating shell: o, 

 marginal fold of mantle: )>. one of the seta-; ( ;, 

 follicle of the same; t, extreme pallial mar- 

 gin.— (Hancock.) 



In all the larger cavities of the body, including not only 

 the greater sinuses of the mantle but also the perivisceral 

 cavity and the cavernous brachia and cirri, are found calcareous 

 spicules of various shapes Which, in some genera, especially Tiik- 



48 



