. Bulletin - United States National Museum. Science. Fig. 11.—Coeynotrypa abrupta. a and 6, portions of THE TYPE-SPECIMEN, X9 AND X20, INCRUSTING A FRAG- MENT OF Rhynchotrema capax. Richmond group, Iron Ridge, Wisconsin. proximal stolonal portion is almost threadlike, being not more than mm. in width. Tliis diameter is retained until the anterior third or fourth is reached, when the zocscium abruptly swells, with an angle of divergence of 50°, and becomes rounded, with a diameter of to mm. An average zooecium and its stolon is mm. long, but in individual zooecia of the same
. Bulletin - United States National Museum. Science. Fig. 11.—Coeynotrypa abrupta. a and 6, portions of THE TYPE-SPECIMEN, X9 AND X20, INCRUSTING A FRAG- MENT OF Rhynchotrema capax. Richmond group, Iron Ridge, Wisconsin. proximal stolonal portion is almost threadlike, being not more than mm. in width. Tliis diameter is retained until the anterior third or fourth is reached, when the zocscium abruptly swells, with an angle of divergence of 50°, and becomes rounded, with a diameter of to mm. An average zooecium and its stolon is mm. long, but in individual zooecia of the same zoarium the threadhke proximal portion may range in length from less than mm. to 1 mm. The swollen anterior zooecial portion, however, is fairly constant in its measurements, as no devia- tion from a width ranging be- tween mm. and mm., and a length of mm. to mm. has been observed. The apertures are round, subterminal, bordered by a slightly elevated rim, and small, averaging only about mm. in diameter. Corynotrypa ahrupta is easily distinguished from all other species of the genus by the narrow stolon and the very abrupt swelling of the zooecium proper. In related species such as C. injiata (Hall) and C. delicatula (James), the angle of divergence is less, giving a different shape to the zooecium as a whole. The extreme variation in the length of the narrow proximal portion is noted above, and is indicative of the fact that this part of the zooecium is the least stable in simple species of Cyclostomata. Occurrence.—The American speci- men illustrated in figure 11, upon which the species is based, incrusts a fragment of RTiyncJiotrema capax and was found in the liighest beds of the Maquoketa shale of the Richmond group, at Iron Ridge, Wisconsin. The Russian examples assigned to the species were found associated with Calapcecia cribriformis Nicholson, Halysites sp., Streptelasma, and other fossils of the coral bed, in the Lyckholm limestone (Fl
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