296 MANUAL OF ZOOLOGY. 



Leuckhart. Amongst the more striking facts adduced in sup- 

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

 and worm-Hke 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 

 Brachiopoda 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. Terehratulidce. 



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 som? solid object. Foramen partially surrounded 

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

 partially supported by calcified processes, usually in the form of a looj:), 

 and always fixed to the dorsal valve. 



Genera. — Terebraiula (witli Terebratulina, and Waldheimia), Tere- 

 hratella, Stringocephahts, ^-'c, ** 



Fam. II. ThecididcE. 



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 cavfty ; cirrated arms folded upon themselves, 

 and supported by a calcareous loop. 



Genus. — Thecidium. 

 Fam. III. Spiriferida. 



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

 punctated Or unpunctated. Arms largely developed, and entirely 

 supported by a tliin, shelly, sjDirally rolled lamella. 



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

 Fam. IV. Koninckidai, 



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

 supported by two lamellse, spirally coiled. 



Genus. — Koninckia. 

 Fain. 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. 

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

 pair of short, curved, shelly processes. Shell-structure fibrous and 

 impunctate. ,, 



Genera. — Rhynchonella, Pentamenis, Porambonitcs, &=( 

 Fam. VI. Strophomenida:. 



Animal unknown ; some probably free, others attached, during the 

 whole or a portion of their existence, by a" muscular peduncle. No 

 calcified supports for the arms. Shell v/ilh a straight hinge-line, and 

 a low triangular area in each valve. Shell-structure fibrous and 

 punctated. 



Genera. — Orlliis, Ortlihina, Slropliomcna, and Leplana. 



