3 I 6 MANUAL OF ZOOLOGY. 



tion as to the close relationships subsisting between the Brachio- 

 poda and Polyzoa, and until recently most naturalists held that 

 both these groups had strongly-marked affinities with the La- 

 mellibranchiata. This view is still held by the generality of 

 naturalists ; but recently Mr Edward Morse has brought forward 

 evidence to show that the Brachiopoda and Polyzoa are most 

 nearly related to the Tubicolar Annelidas ; and this opinion 

 has been previously advanced as regards the latter group by 

 Leuckhart. Amongst the more striking facts adduced in sup- 

 port of this view may be mentioned the assertion that the long 

 and worm-like peduncle of Lingula pyramidata is normally 

 encased in a sand-tube resembling that of a Tubicolous Anne- 

 lide. The peduncle of this form is also contractile and hollow, 

 admitting the blood into its interior, and the blood is stated to 

 be red. In the meanwhile, however, the affinities between the 

 Trachiopoda and Polyzoa, on the one hand, and the Tunicata 

 on the other, are too strong to allow of our unhesitating accept- 

 ance of this sweeping change. 



CLASSIFICATION OF THE BRACHIOPODA (AFTER DAVIDSON). 

 CLASS BRACHIOPODA. 



Fam. I. Terebratulida. 



Shell minutely punctate ; ventral valve with a prominent beak per- 

 forated by a foramen for the emission of a muscular peduncle, whereby 

 the animal is fixed to some solid object. Foramen partially surrounded 

 by a deltidiutn of one or two pieces. Oral appendages entirely or 

 partially supported by calcified processes, usually in the form of a loop, 

 and always fixed to the dorsal valve. 



Genera. Terebratula (with Terebratulina and Waldheimia), Tere- 

 bralella.) Stringocephalus, &c. 

 Fam. II. Thecidid(e. 



Shell fixed to the sea-bottom by the beak of the larger or ventral 

 valve ; structure punctated. Oral processes united in the form of a 

 bridge over the visceral cavity ; cirrated arms folded upon themselves, 

 and supported by a calcareous loop. 



Genus. Thecidium. 

 Fain. III. Spiriferidtz. 



Animal free, or rarely attached by a muscular peduncle. Shell 

 punctated or unpunctated. Arms largely developed, and entirely 

 supported by a thin, shelly, spirally rolled lamella. 



Genera. Spirifer, Spiriferina, Cyrtia, Athyris, &c. 

 Fam. IV. KoninckinidcE. 



Animal unknown. Shell free ; valves unarticulated (?). Oral arms 

 supported by two lamellae, spirally coiled. 



Genus. Koninckia. 

 Fam. V. Rhynchonellida. 



Animal free, or attached by a muscular peduncle issuing from an 

 aperture situated under the extremity of the beak of the ventral valve. 

 Arms spirally rolled, flexible, and supported only at their origin by a 



