RECENT BRACHIOPODA 261 



hasia, 1 ; Cistella, 6 ; Cryptopora, 2 ; Dallina, 3 ; Hemithyris, 6 ; Laqueus, 

 4 ; Liothyrina, 6 ; Magellania, 4 ; Megathyris, 3 ; Miihlfeldtia, 3 ; Platidia, 

 2; Terebratalia, 4; Terebratella, 3; Terebratulina, 7, and Thecidium, 2). 



Below 600 feet and above 1,000 feet appear 17 additional articulate 

 species ( Acanthothyris, 1 ; Cistella, 3 ; Dallina, 2 ; Hemithyris, 1 ; Kraus- 

 sina, 4; Liothyrina, 2; Macandrevia, 2; Platidia, 1, and Terebratu- 

 lina, 1). 



There are 11 deep-water forms, not one of which extends above 1,000 

 feet of depth or goes into the abyss. As a rule they are, like the abyssal 

 forms, thin-shelled animals, but do not average as small as the true 

 deep-sea species. These are the rhynchonellids Hemithyris gerlachi 

 (243-270 fathoms), H. racovitzw (270), and Basiliola heecheri (200- 

 313), occurring off western Hawaii; the terebratulids, Dyscolia ivyvillii 

 (385-845), Liothyrina antarctica (385), L. sphenoidea (215-1,090), 

 L. subquadrata (500-600), L. winteri (360), Milhlfeldtia echinata (346- 

 423), Platidia (?) incerta (390-1,120), and Terebratulina valdivice 

 (392). 



Of typical abyssal forms that have strayed far from the continents 

 there are but five: the discinid Pelagodiscus atlanticus (200-2,465) ; the 

 rhynchonellid Hemithyris strehli (2,035-2,084) ; the terebratulids Chli- 

 donophora chuni (865-1,220) ; C. incerta (292-1,850), and Liothyrina 

 (?) wyvillii (1,035-2,900). To these must be added 13 other forms 

 that are also abyssal in habitat, but are still situated close to the conti- 

 nents. These are the rhynchonellids Hemithyris craneana (1,175) ; the 

 terebratulids Frieleia halli (599-984), Eucalathis (the 4 species of this 

 genus, 300-2,588), Liothyrina clarheana (1,175-2,035), L. mosleyi (210- 

 2,222), Macandrevia craniella (1,175), M. diamantina (1,175-2,222), 

 M. tenera (1,450), Magellania wyvillii (2,160), and Terebratulina (?) 

 dalli (1,875). All of these abyssal species are small in size or below the 

 average of their genera, and have very thin, fragile shells. 



These figures giving the bathymetric range of recent brachiopods teach 

 us that fully 80 per cent inhabit waters shallower than 1,000 feet, and 

 over 70 per cent live above 600 feet. Brachiopods therefore are, as a 

 rule, significant of shallow water and of continental or epicontinental 

 seas. 



INARCTICULATA GENERA 



Let us now examine into the detailed bathymetric range of the 33 liv- 

 ing brachiopod genera, to see if anything can be learned from their dis- 

 tribution that will give guidance as to the depths at which the fossil 

 forms lived. We have seen that but 5 species are restricted to the strand- 



