LIVING BRACHIOPODA. 315 



Note of explanation. I have used the terms Testicardines and Ecardines as they are 

 in common use, and the forms they include are well known. They parallel Owen's divi- 

 sions of Arthropomata and Lyopomata, as well as those of Huxley's Articulata and Inarti- 

 culata. The names proposed by King, Gill ('73) , and others also include the same divi- 

 sions. As Beecher ('92) says in referring to Huxley's definitions, " these names may be 

 conveniently retained as two divisions or sub-classes, but they fail to express the true rela- 

 tionships of the various groups included in them," so the terms Testicardines and Ecar- 

 dines are used simply as convenient names to designate certain well known forms. In 

 justice to Beecher, I must say here that the classification proposed by this naturalist rests 

 on such a profound and varied comparison of the fossil as well as the recent forms that it 

 may well be accepted as the latest and best expression of the relationships of these ani- 

 mals. If he were compelled to bring his four groups into two divisions, however, he 

 would certainly group Atremata and Neotremata together, which would give us the Inarti- 

 culata, or the Ecardines, and his Protremata and Telotremata, which would give us the 

 Articulata or Testicardines. The works of Beecher and Schuchert are above all the most 

 painstaking and philosophical studies of these fascinating animals yet given. 



In referring to Glottidia pyramidata I have used the generic term only, to avoid the 

 repetition of the long specific name. In every instance, then, the word Glottidia is used 

 for the species pyramidata. Judging from the well marked characters of the shell of 

 Glottidia albida, a Pacific coast form, I have no doubt that the internal structure will be 

 found to be the same as in the Atlantic coast species. 



For convenience of reference I have used the term coelomic cavity without asserting 

 that it is the true coelom. In order to be explicit, I have at other times lised the terms 

 perigastric and perivisceral cavity. I have also used the word blood to indicate the only 

 circulating fluid I have seen in Uving Brachiopoda. Perivisceral fluid, perienteric fluid, 

 chylaqueous fluid, and other terms might be more exact or perhaps less committal, but 

 when the term blood is used it will be understood to imply the fluid, charged with various 

 corpuscles, which is seen circulating within the tissues. 



References to the plates and figures are given by numbers only ; thus 49 : 3 means 

 plate 49, figure 3. In this way is avoided the repetition of the words plate and figure, 

 or their abbreviations. 



In aU cases, unless otherwise explained, the figures are drawn with their dorsal 

 region uppermost, if seen from the front or side; and if seen from the dorsal or ventral 

 side, the anterior region is uppermost. With two exceptions, all the figm-es are exact 

 copies of my original sketches ; hence many of the drawings are incomplete, some of 

 them being mere sketch memoranda. 



