MOLLUSCOIDA, 



Class BRACHIOPODA. 



The animals, and more especially the shells of this class of 

 molluscoids, were for a long period regarded as belonging to 

 true mollusca, and so uniforml}^ are they still the objects of con- 

 chological study that a treatise upon that science would be very 

 incomplete for practical use, if the Brachiopoda were excluded. 

 On the other hand, the two other classes of Molluscoida, the 

 Tunicata and Bryozoa, are beyond the usual scope of concho- 

 logical investigation, and as this work would be considerably 

 increased in bulk and cost by the description and illustration of 

 their systematic groups, they are omitted. 



Steenstrup, Morse, Kowalevsky and other eminent investi- 

 gators, have concluded, mainly from embryological data, that 

 the brachiopods form a portion of the subkingdom Annulosa, 

 and are nearly related to the annelids or worms. Dall and 

 Stoliczka have maintained the moUuscoid affinities of the class, 

 Thomas Davidson, who has made a specialty of the study of the 

 Brachiopoda, summarizes the arguments of these naturalists and 

 thus concludes : 



" No one can doubt that the brachiopods and Amphitrites 

 possess many important characters in common after perusing the 

 admirable observations upon the subject contained in Prof. 

 Morse's memoir ; but at the same time, as was remarked to me 

 by Prof. Verrill, almost any invertebrate group may be annelid- 

 elized by overrating certain points of its affinities ; and it 

 seems to me that one must not place entire confidence in any 

 classification which is founded to so great an extent on embryo- 

 logical characters." 



Huxley writes : " The acceptance of the view originally pro- 

 pounded by Steenstrup and so ably urged by Professor Morse, 

 respecting the affinities of the brachiopods with the worms, does 

 not to my mind weaken the opinion I have always held as to 

 their affinities with the Bryozoa on tne one hand, and with the 

 higher Mollusca on the other." 



