506 



Forty- fifth Report on the State Museum, 



or vertical extension of the mantle which incloses the viscera is 

 highly muscular and leaves an impression on the valves. In 

 ancient and fossil forms of Lingtjla it is evident that the arrange- 

 ment was similar to that of living species, and though specimens 

 have been rarely seen which show the muscular scars clearly, a 

 few have been recorded which have retained the scars with great 

 distinctness. In Obolus, Mickwitz finds that, while the general 

 arrangement of the scars is similar to that of Linguxa, the 

 umbonal diductor is simple at its insertion in the brachial valve, 

 and divides in crossing the cavity. This author also ascribes two 

 distinct pairs of scars to the rotators, one to the adductors and 



Fig. 121.— Extremity of ad- 

 ductor muscle of Magella- 

 niaaustralis. a,contractile 

 portion ; b, tendinous por- 

 tion. (Hancock.; 



Fig. 122.— Non-striated 

 muscular fibers of 

 Magellania av stra- 

 its. (Hancock.) 



Fig. 123.— Striated 

 posterior adductor 

 or muscular fibers of 

 of Magellania aus- 

 tralis. (Hancock.) 



another pair which may be either adductors or a third pair of 

 rotators. 



There are some differences in the appearance of the muscular 

 bands in the articulate and inarticulate brachiopods, those of the 

 former tapering from origin to insertion, while in the latter they 

 are of more equal thickness throughout. The muscular libers are 

 smooth, except in the posterior adductor bands where they striated. 



Alimentary System. 



The mouth is a simple orifice located centrally at the base of 

 the fleshy brachia. In Mkuathyris the oval or buccal area is very 

 broad, but in most brachiopods it is narrowed to a simple groove, 



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