48 



DE. T. DAVIDSON ON RECENT BRACHIOPODA. 



this chamber, aud terminates at the anterior extremity of the lateral portion of the loop, 

 forming what may be designated as the brachial pouches. The cirri are tindoubtedly 

 contractile to some extent, and are also endowed Avith the power of motion individually, 

 as proved by the observations of Mr. Barrett. It would likewise appear that the 

 entire fringe of cirri can be elevated or depressed, there being ample means provided for 

 tlie purpose." Many other highly important details have been recorded by Owen, 

 Gratiolet, and Hancock, which I regret I am unable to reproduce. 



Mr. Hancock states, at p. 811 of his memoir, that "the mouth, in all the Brachiopods, 

 as previously stated, is situated in the brachial groove, at the posterior junction of the 

 arms, and is a simple, oval, transverse slit, or orifice devoid of any armature. In 

 JF. australls there is, however, a slight bulging-out of the posterior wall immediately 

 within the orifice, which is somewhat like the valvular appendage of Phimatella, and may 

 perhaps assist in swallowing. The alimentary tube assumes the form of a siphon bent in 

 the vertical plane, the arch turned towards the dorsal valve ; the oesophagus represents 

 the short, the stomach and intestine the long arm." 



There is no anal outlet in this species. According to the same author, the mesentery 

 is divided into two portions, the dorsal and ventral : it sustains the alimentary canal in 

 the vertical plane, and altogether with it divides the anterior portion of the chamber 

 into lateral halves. The gastro-parietal bands are three in number, two lateral and one 

 median. 



In W. flaveseens, Mr. Hancock says, " the genitalia are formed of thick bands, 



Fig. 8. 



Lateral view of the Viscera of WaJdheimiaJiavescms, after Hancock, 

 n, anterior layer of mantle ; b, posterior layer; c, anterior walls of the body between the mantle-lobes ; (7, arms; 

 p, gullet ; q, stomach, with cut biliary ducts of the left side ; r, right hepatic mass : s, intestine ending 

 ca'cally between j and k ; v, so-called " auricle " of the right " pseudo-heart," the left being almost wholly 

 removed ; w, pyriform vesicle fixed to the back of the stomach, and probably performing the function of a 

 true heart ; r, oesophageal ganglia. (This figure is also given by Huxley on page 28 of his ' Introduction to 

 the Classification of Animals,' 1869.) 



