466 



Prof. Owen, and believes that the latter observer has mistaken the 

 blood-seinuss for muscles. 



The author doubts whether the spiral coil can be unwound, and 

 conceives that the muscular fibres described, are chiefly for the pur- 

 pose of giving firm support to the grooved ridge on which the cirri 

 and brachial fold are seated, and thus affording the complex mus- 

 cular fibres which the ridge contains a better fulcrum whence to act 

 upon the cirri. 



In Terebratulina caput-serpentis, which possesses no calcareous 

 loop, the pallial lobe connecting the produced and reflected portions 

 of the arms is strengthened by calcareous spicula, which are so 

 numerous as to preserve the shape of the part even when the animal 

 basis is removed. 



In Lingula the arms contain two canals ; one, the anterior, being 

 the equivalent of the single canal in Rhynchonella, and, like it, ter- 

 minating at the side of the oesophagus in a blind sac. The posterior 

 brachial canal probably communicates with the perivisceral cavity and 

 exhibits a peculiar arrangement of muscles, by whose action perhaps 

 the arm can be exserted. 



In addition to those parts of the alimentary canal and its append- 

 ages which are already known in the articulated Brachiopoda, the 

 author describes a short median gastro-parietal band arising from the 

 upper surface of the stomach and passing upwards and backwards to 

 the dorsal parietes a little in advance of the hinge-plate. With 

 regard to the existence or absence of an anal aperture in the articu- 

 lated Brachiopoda, the writer states : " I have made numerous dis- 

 sections under a powerful doublet, and have removed the part and 

 examined it with a microscope : I have filled the tube with fluid 

 as the fingers of a glove with air, and by pressure have attempted to 

 force a passage : I have tried injections ; but have equally, on all 

 occasions, failed to discover an outlet, and have only succeeded in 

 demonstrating more and more clearly the csecal nature of the ter- 

 minal extremity of the alimentary canal. Therefore, how much 

 soever it may be opposed to analogy and to authority, the fact must 

 be recorded there is no anal orifice in Waldheimia, Terebratulina, 

 or in Rhynchonella." 



In Lingula, as in the articulated Brachiopoda, the first inflection 

 of the intestine is towards the ventral surface, but the alimentary 



