DE. T. DAVIDSON ON EECENT BEACHIOPODA. 65 



cranium (PI. XIII. figs. 1, 2). lie says that in Waldhehnia cranium, and in TerebratuUna 

 caput-seryentis, "the dorsal adjuster muscles are not attached to a hinge-plate, as in 

 W. australis, but have their insertions in the ventral valve itself, and are very large and 

 powerful. In both species the superior extremities of these muscles are seen at the 

 surface of the animal, on each side of the median line, elongated in the antero-posterior 

 direction and extending between the occlusors almost as far forward as the anterior 

 margins. . . . The divaricators and the accessory divaricators in W. cranium are likewise 

 united in the same manner as in the species before alluded to." Mr. Hancock further 

 observes that " the arms in W. cranium and T. caput-serpentis are disposed in the same 

 manner as in W. australis ; and in the former the calcareous loop is precisely similar to 

 that of the latter ; but in T. caput-serpentis it is very much reduced, the extended lateral 

 portions having almost entirely disappeared, little more than the transverse portion 

 existing ; and this, together with the crural processes, which are united below across the 

 median line, forms a collar upon which the bases of the arms rest. 



" In W. cranium the intestine is very short, terminating in a blind sac before it 

 reaches the ventral wall of the perivisceral chamber. It tapers gradually to a point, 

 which is rounded, and suspended in its place by the mesentery. The mucous membrane, 

 lining the intestinal tube of If. cranium, is exceedingly thick, and produced into five 

 or six excessively stout, longitudinal folds, which in transverse sections exhibit a pyra- 

 midal contour, their apices almost meeting in the centre of the tube .... In W. cranium 

 the genitalia are arranged as in W. australis, only the bands do not extend so far 

 forward, and are of a pale yellow colour. The red matter is also present, sprinkling the 

 surface with distant round spots. The bands arc very finely granular, and in no instance 

 have I detected eggs in them. It is therefore probable that those examined were out 

 of season." Mr. Ilancock also observes: — "There is no modification to note in the 

 perivisceral chamber in any of the Terebratulidaj that I have had an opportunity of 

 examining. The pallial sinuses, however, vary in several species. Thus in W. cranium, 

 though there are still four such sinuses in each lobe, the trunks are proportionately 

 smaller, and more nearly of a size ; the branches are fewer and more attenuated, but, as 

 in the other species, divided dichotomously twice or thrice, without any very marked 

 symmetry." 



The animal of Waldheimia cranium although differing in some unimportant details 

 from that of Waldheimia flavescens is essentially similar. In both the loop is the same, 

 and there is no difference, of any great importance, in the shape of the shell. I therefore 

 question the necessity of bm'dening the nomenclature by placing W. cranium and 

 IF. Jiavescens in difi'erent and distinct genera. But as the contrary view has been 

 expressed by such excellent observers as Prof. W. King, Douville, Zittcl, Waagen, 

 Deslongchamps, and others, I would not wish to press my own views too far, in 

 opposition to theirs. M. DouvUle seems to think that W. cranium possesses a special 

 development of its loop ; while M. E. Deslongchamps, at page 1-il of his Etudes 

 critiques sur les Brachiopodes,' 1881-, difiers from M. Douville, and expresses his opinion 

 that the general appearance of the loop of Macandrcvia cranium is actually the same as 

 that attributed to JFaldheimia. The shape of the principal stems show s the greatest 



SECOND SEUIES.— ZOOLOGY, VOL. IV. U 



