107 



to suppose that some cloacal aperture must exist in the neighbour- 

 hood of the pedicle. 



The existence of any such aperture, however, has recently been 

 denied with great justice by Professor Owen. 



The result of my own repeated examinations of Rhynchonella psit- 

 tacea and of Waldheimia flavescens is 1. that the intestine does not 

 terminate on the right side of the mantle as Professor Owen describes 

 it, but in the middle line, as Mr. Hancock describes it in Waldheimia, 

 while in Rhynchonella it inclines, after curving upwards, to the left 

 side; and 2. that there is no anus at all, the intestine terminating 

 in a rounded caecal extremity, which is straight and conical in Wald- 

 heimia, curved to the left side and enlarged in Rhynchonella. 



I confess that this result, so exceptional in its character, caused 

 me no small surprise, and I have taken very great pains to satisfy 

 myself of the accuracy of my conclusion ; but notwithstanding the 

 strong prejudice to the contrary, to which the known relations of the 

 anal aperture in Lingula gave rise, repeated observation has inva- 

 riably confirmed it. 



Professor Owen's statement is, that in Rhynchonella (Terebratuld) 

 psittacea " the intestine inclines to the right side and makes a slight 

 bend forwards before perforating the circumscribing membrane in 

 order to terminate between the mantle lobes on that side." On the 

 Anatomy of the Brachiopoda, p. 152. 



I find, on the contrary (figs. 1 and 2), that the intestine passes 

 at first straight downwards in the middle line, as in Waldheimia, but 

 instead of terminating in a rounded tapering extremity as in that 

 genus, it bends upwards and then curves round to the left side, 

 forming a sort of free caecum in the visceral cavity. My reasons for 

 believing that it is a free caecum are these : in the first place, no 

 anal aperture can be detected in the mantle cavity, either on the 

 right or left sides, although the small size of the animal allows of 

 its being readily examined uninjured, with considerable magnifying 

 powers. 



Secondly. If the shell be removed without injuring the animal 

 and the visceral cavity be opened from behind by cutting through its 

 walls close to the bulb of the pedicle, it is easy not only to see that 

 the disposition of the extremity of the intestine is such as I have de- 

 scribed it to be, but by gentle manipulation with a needle to convince 



