Characters o/'Lingula anatina. 9 



or no impressions ; and it is the same in a number of extinct 

 families ; from which it may be concluded that the relation of 

 the latter to the Lingulids must be remote. 



One reason why the splanchnocoele of Lingula is much larger 

 than usual is that it contains the genitalia. These organs, or 

 perhaps more correctly the ovaries, in the Terebratulids &c. 

 are for the most part located in the brachiocoele, leaving impres- 

 sions occasionally beautifully displayed in fossils; as maybe seen 

 in Davidson's figures of Orthis Bailyana^ 0. rustica^ 0. calli- 

 gramma*, and several others, also in some recent species. 

 The ovaries are generally located on each side of the splanch- 

 nocoele ; it might therefore be inferred that the spaces similarly 

 situated in certain fossils, as the Trimerellids, were the seat 

 of these organs. Judging, however, from what is seen in 

 Lingula, the spaces referred to may with more reason be taken 

 to represent the pleurocoeles. 



Brachiocoele or brachial chamber. — The anterior prolonga- 

 tion of the dorsal surface of the splanchnocoele causes this 

 chamber to be much smaller in the dorsal than in the ventral 

 valve. Its most prominent contents are the brachial append- 

 ages (fig. 2, r), which are spii-al, and originate in the anterior 

 parietal, nearer to the dorsal than the ventral valve. The 

 point or apex of the spiral is turned or directed toward the 

 ventral valve, as in other recent Palliobranchs. The arms are 

 too much removed from the inner surface of either valve to 

 produce any impression, as is the case in certain fossils, 

 notably Davidsonia Verneuili'f, Productus giganteus\, and 

 Strophomena Jukesii^. If similar impressions occurred in 

 Lingula they would of course show that the arms had been 

 turned towards the ventral valve : it is remarkable, however, 

 that in the fossils referred to these organs appear to have 

 been turned towards the opposite or dorsal valve. 



The mantle-lobes forming the dorsal (upper) and ventral 

 (under) surfaces of the chamber are well characterized by the 

 vascular system. Both lobes are traversed by a pair of 

 primary vessels (p) that run forward from the anterior parietal, 

 a member from each of its sides : gradually approximating in 

 their progress, without becoming united, they terminate, the 

 dorsal pair at about a quarter of an inch, and the ventral pair 

 at about twice this distance, from the margins of the chamber. 



* British Silurian Bracliiopods, pi. xxix. fig. 20, pi. xxxiv. fig. 16, 

 pi. XXXV. tig. 12. 



t Davidson, ' Introduction to Fossil Brachiopoda,' pi. viii. figs. 187 & 

 188. 



X King, ' Monograph of Permian Fossils,' pi. xix. fig. 2. 



§ Davidson, ' Monograph of British Silurian Brachiopoda,' pi. xxxvii. 

 figs. 25 & 26. 



