lORDER III 



TREPOSTOMATA 



337 



Rhombotrypa U. aiid B. Siluriaii. Petalotrypa and IHscoirypa Ulr. Ordovician 

 to Devon iaii. 



Family 6. Halloporidae Bassler {Galloporidae Ulricli). 



Zoaria ramose, suh-frondescent, massive or discoidal. Zooßcial apertures generally 

 sub-circular and separated more or less completely hy angular mesopores ; at other times 

 polygonal, when fhe mesopores are few or wanting. Zocecial tuhes thin-walled, attaining 

 their füll size sloivly. Acanthopores wanting. Ordovician to Devonian. 



In this faniily the proximal ends of thetubes arising in the axial or "immature" region 

 liave the character of mesopores. The diaphragms are rather closely arranged in the taperiiig 



Fig. 49U. 



HaZlopora ramosa (E. and H.). Ordovician (Cincinnati Group); Cincinnati, Ohio. A, Zoarium, natural 

 size. B, Surface slightly magnified. C, Tangential .section, parallel to external surface, 20/j. j)^ Vertical 

 section, 20/^. ((^,< and D alter Nicholson.) 



proximal end, then few or wanting for a considerable distance, and finally become crowded in 

 the peripheral or mature region. 



Hallopora Bassler {Gallopora Hall preoccupied) (Figs. 490, 491). Zoaria usually 

 ramose and biisliy, tlie branclies often anastomosing. Apertures closed in tlie perfect 

 State by perforated, often ornainented, Covers, which are left behind, as growtli proceeds, 



Fi(i. 491. 

 A, B, Hallopora eleqantula (KaU). Niagara ; Indiana. Vertical and tangential seetions, "/j. C, D, H. imdti- 

 tabulata Ulr. Lower Trenton ; Minnesota. C, Vertical section, v/i. D, Surface having zooecia open (7/i), and 

 preserving zoo?cial covers (i-*/i). 



to form floors (diaphragms) of succeeding layers. Zocecial tubes of two sizes in the axial 

 region, the larger ones with six to eight sides, the smaller set four- or five-sided. 

 Ordovician to Devonian. 



Halloporina, nom. nov. (proposed for Calloporina Ulrich and Bassler, preoccupied 

 by Neviani in 1895). Like Hallopora but diaphragms wanting and walls strongly 

 crenulated. Ordovician. 



Calloporella Ulr. Silurian ; North America. 

 VOL. I Z 



