[ 66 J 



appendages, but very much less developed. They assumed different 

 shapes in different genera, and were supported, or otherwise, by the 

 more or less complicated calcified skeleton, already described. 

 These two long, bent, or spirally convoluted organs, occupied the 

 larger portion of the cavity of the shell, and were mainly composed 

 of a membranous tube, fringed un one side with long flexible cirri. 

 The brachial appendages occupied, therefore, nearly the entire 

 pallial cavity, but were not capable of being protruded iu those 

 families and genera in which they were folded upon themselves, 

 or supported by a calcareous skeleton. In Rhynchonclla, 

 where the elongated spiral arms were but slightly supported 

 at their origin by two short projecting calcareous processes, 

 they could, at the will of the animal, be iiurolled, and 

 protruded to some distance beyond the margins of the shell, and, 

 when forcibly stretched out, were said to be more than four times 

 the length of the shell, and to support some 3.000 cini. It must, 

 however, remain for ever uncertain whether, in those extinct 

 genera, such as Spirif er and Atrypa, where the spirally coiled fleshy 

 arms were supported throughout their entire length by a calcifled 

 skeleton, the animal could protude its brachial appendages beyond 

 the margin of the valves. In some families, Hhynchonellidce, 

 FrodnctidcB, the arms are spiral and separate, in others, Linfjulidw, 

 only at their extremities, and it was almost certain that these 

 beautiful organs by means of their cirri and the cilia, with which 

 they were doubtless furnished, were not only instrumental incany- 

 ing floating nutrimental particles or minute organisms to the 

 mouth, but were subservient to the functions of respiration. 



MOUTH : HEARTS. 



The mouth conducted by a narrow oesophagus t<^ a simple 

 stomach, which was surrounded by a large granulated liver. 

 Owen's " hearts " had been found to be oviducts, while the true 

 heart wo\ild consist of a pyriform vesicle, appended to the dorsal 

 surface of the stomach. 



MTJSCLES. 



He must next speak of the muscular system, and as the num- 

 ber and position of these muscles differed materially in the two 

 great divisions into which the Brachiopoda had been separated, and 

 to some extent also in the different crenera of which each division 



