270 CONFERENCE ON PALEOZOIC PALEOGEOGRAPHY 



stricted to Atlantic Gondwana. Into this realm (below 1,000 fathoms) 

 also enter the shallow-water genera Cistella (20-1,622, Cretaceous), 

 Cryptopora (25-2,200), Gwynia (8-2,200, Pleistocene), Hemithyris 

 (15-2,084, Pliocene), Liothyrina (6-2,900, Pliocene), Macandrevia 

 (5-2,222, Pliocene), Magellania (0-2,160, Jurassic), Terebratella 

 (5-1,450, Jurassic), and Terebratulina (3-1,875, Jurassic). 



BOREAL REGION 



There are 6 genera typical of this region. Of wide distribution in 

 northern waters is Dallina. It is best developed about Japan (3 spe- 

 cies), and from here it probably spread into Arctic waters and along the 

 eastern shores of the Pacific southward across Panama (previous to 

 Upper Miocene time) into the Antillean region. In Arctic waters the 

 genus occurs at Spitzbergen, and thence south to North Africa, but no 

 relicts are found today in any of the Atlantic oceanic islands. Laqueus 

 and Terebratalia, both also at home in the North Pacific, and probably 

 as old as Dallina, did not get into the Atlantic by either the northern or 

 Panama routes. Acanthothyris, widely distributed in the later Meso- 

 zoic, is now restricted to Japan. 



Hemithyris is probably also of boreal origin where the family Rhyn- 

 chonellid^ is best developed since the Siluric. The present distribution 

 of this genus is nearly world-wide, but with peculiar and extensive geo- 

 graphic lacunae due to causes not yet understood. The genus has 11 

 species, and of these 5 occur in boreal waters, 4 in austral, 1 in Oceanica 

 {H. grayi), and 1 {H. strebli) is a deep-sea form occurring in mid- 

 Pacific. Of boreal species none occur off the United States or in An- 

 tillean waters. On the Pacific side of the two Americas but a single 

 specimen has been taken in the Gulf of Panama {H. craneana) at a 

 depth of 1,175 fathoms, and another form, Frieleia halli, occurs from 

 San Diego, California, to Washington. H. psittacea is circumpolar in 

 its distribution, attaining Japan (var. woodwardi; also H. lucida), Una- 

 laska to Shumagins, Gulf of St. Lawrence, Norway south to Shetlands, 

 and fossil even to Sicily. In the northeastern Atlantic occurs the non- 

 plicate H. cornea. In Antarctic waters there are 3 species, with a fourth 

 one in the New Zealand area. These forms seem to have spread from 

 Japan south through Oceanica, and thence by way of New Zealand into 

 Antarctica. 



AUSTRAL REGION 



There are 6 genera restricted to this region. Of more or less wide 

 distribution in southern waters are Agulhasia (off South Africa), Kraus- 



