No. 1797. 



NEW TVBULIPOROID RRY0Z0A—BA8SLER. 



517 



greater angles of divergence and their zooecia are therefore corre- 

 spondingly more swollen. 



Occurrence. — Specimens of 0. inflata are generally abundant in all 

 of the middle and upper Ordovician and earliest Silurian (Richmond) 

 formations of North America. Recently its geographic range has 

 been extended by the discovery of typical examples in the middle 

 Ordovician (Wesenberg) limestone, at Wesenberg, Esthonia, Russia. 

 The original types came from the Trenton rocks of New York, where 

 the zoarium is of more delicate growth than in the higher formations. 

 The forms from the several Cincinnatian formations have a very lux- 

 uriant growth, one network of zooecia covering another until dense 

 clusters result. 



Plesioty pes. —C&t. nos. 43261, 43262, 54146, 54149, 54162, 54169, 

 54202, 57108, U.S.N.M. 



CORYNOTRYPA ABRUPTA, new species. 



Zoarium adnate, consisting of frequently branching, elongated, 

 rather large, clavate zooecia, much swollen at the anterior end. The 

 tubular proximal sto- 

 lonal portion is almost 

 thread-like, being not 

 more than 0.04 mm. 

 in width. This diam- 

 eter is retained until 

 the anterior third or 

 fourth is reached, 

 when the zooecium 

 abruptly swells, with 

 an angle of diverg- 

 ence of 50°, and be- 

 comes rounded, with 

 a diameter of 0.20 to 

 0.25 mm. An average zooecium and its stolon is 1.0 mm. long, but in 

 individual zooecia of the same zoarium the thread-like proximal portion 

 may range in length from less than 0.10 mm. to 1 mm. The swollen an- 

 terior zooecial portion, however, is f ahly constant in its measurements, 

 as no deviation from a width ranging between 0.20 mm. and 0.25 mm., 

 and a length of 0.32 mm. to 0.40 mm. has been observed. The aper- 

 tures are round, subterminal, bordered by a slightly elevated rim, 

 and small, averaging only about 0.09 mm. in diameter. 



Corynotrypa ahrupta is easily distinguished from all other species of 

 the genus by the extremely narrow proximal portion and the very 

 abrupt swelling of the anterior end of the zooecium. In related 

 species such as C. injlata (Hall) and C. medialis, new species, the 

 change from the proximal to the anterior end is less abrupt, but in 



Fig. 16.— Corynotrypa abkupta. a and 6, portions of the 



TYPE-SPECIMEN, X9 AND X20, INCRUSTING A FRAGMENT OF RHYN- 

 CHOTREMA CAP AX. RICHMOND GROUP, IRON RiDGE, WISCONSIN. 



