332 CONTRIBUTIONS TO THE ANATOMY OF THE BRACHIOPODA 



above the mouth, one on each side of the hver (i). It is these latter 

 which Professor Owen describes, while he has apparently overlooked 

 the other two, at least he says (speaking as I presume of Rhyncho- 

 nelld) [1. c. p. 148) that the venous sinuses "enter the two hearts, 

 or dilated sinuses which are situated exterior to the liver, and in 

 T. Chilensis and T. Sowerbii just within the origins of the internal 

 calcareous loop." 



The fact is, that while the ilio-parietal bands support two ' hearts '' 

 as usual, the gastro-parietal bands are in relation with two others. 

 The base of the ' auricle ' of the latter opens into the re-entering 

 angle formed by the gastro-parietal band with the parietes, while 

 its apex is directed backwards to join the ventricle, which passes 

 downwards and backwards along the posterior edge of the posterior 

 division of the adductor muscle. 



The auricles in Rhynchonella are far smaller, both actually and 

 proportionally, than in W aldlieimia. They exhibit only a few 

 longitudinal folds, and not only present the same deficiency of 

 muscular fibres as those of WaldJieimia, but are so tied by the 

 bands which support them that it is difficult to conceive how 

 muscular fibres, even if they existed, could act. The ' ventricles ' 

 in like manner lie obliquely in the parietes of the body, and simply 

 present villous eminences on their inner surface, which has a yellowish, 

 colour. 



All these ' hearts ' exhibit the same curious relation with the geni- 

 talia in Rhynchonella as in Waldheiviia; that is to sa)-, a 'genital 

 band ' (/) proceeds from the base of the ' ventricle ' and becomes the 

 axis of the curiously reticulated genital organ. But in Rliynchonella 

 the genital bands of the upper genitalia come from their own 

 ' hearts.' 



The arrangement of the genitalia in Rhynchonella is very remark- 

 able. The sinuses have the same arrangement in each lobe of the 

 mantle. The single trunk formed by the union of the principal 

 branches in each lobe opens into the inner and anterior angle of a 

 large semilunar sinus which surrounds the bases of the adductors,, 

 and opens into the visceral cavity. The floor of this great 

 sinus is marked out into meshes by the reticulated genital band, 

 and from the centre of each mesh a flat partition passes, uniting 

 the two walls of the sinus, and breaking it up into irregular partial 

 channels. 



There are the same anastomosing bands uniting the gastro- 

 parietal and ilio-parietal bands on the stomach in Rliynchonella 

 as in Waldheiviia, and a pyriform vesicle of the same nature. 



