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BULLETIN 11, UNITED STATES NATIONAL MUSEUM. 



DITTOPORA COLLICULATA (Eichwald). 



Plate 3, figs. l-4c, 6; plate 11, figs. 7-15; text figs. 188-190. 



Trematopora colliculata Eichwald, Bull. Soc. Nat. Moscou, No. 1, 1856, p. 96. — 

 Schmidt, Archiv. fur d. Nat. Liv-, Ehst- und Kurlands, vol. 2, ser. 1, 1858, 

 p. 228. — Eichwald, Lethsea Rossica, vol. 1, sect. 1, 1860, p. 494, pi. 27, figs. 

 14a_c. — Dybowski, Die Chaetetiden der Ostbaltischen Silur-Formation, 

 1877, p. 72, pi. 2, figs. 4-4c. — Nicholson, The Genus Monticulipora, 1881, 

 p. 233, fig. 48. 



Trematopora cingulata Dybowski, Die Chaetetiden der Ostbaltischen Silur- 

 Formation, 1877, p. 78, pi. 2, figs. 1, 16. 



Trematopora cingulata var. nodosa Dybowski, Die Chaetetiden der Ostbaltischen 

 Silur-Formation, 1877, p. 80, pi. 2, fig. la. 



Trematopora variabilis Dybowski, Die Chaetetiden der Ostbaltischen Silur- 

 Formation, 1877, p. 81, pi. 2, figs. 2, 2a. 



Trematopora variabilis var. complanata Dybowski, Die Chaetetiden der Ost- 

 baltischen Silur-Formation, 1877, p. 83, pi. 2, figs. 3, 3a. 



Trematopora pustulifera Dybowski, Die Chaetetiden der Ostbaltischen Silur- 

 Formation, 1877, p. 80, pi. 2, fig. 6. 



Dybowski has given a lengthy, detailed description of Eichwald's 

 Trematopora colliculata, and more or less extended descriptions of 

 the species and varieties listed above as synonyms. On account of the 

 marked external peculiarities, elongate-oval zooecia with closed 

 interzooecial spaces, Eichwald's illustrations (fig. 188) are sufficient 

 for the identification of his species; moreover, Dybowski has figured 



the internal structure 

 fairly well (see pi. 3, 

 figs. 4-4 &). I have 

 examined over 400 

 specimens with this 

 same internal struc- 

 ture. Of these a small 

 percentage have their 

 maculae raised into 

 rounded monticules, as 

 figured by Eichwald, 

 a large number have 

 their monticules trans- 

 versely elongated, 

 while, finally, in the 

 largest number of 

 specimens the maculae are not raised at all, but are so elongated 

 that they form an encirchng ring about the zoarial branch. Such 

 variation is not unusual in species of Batostoma and other genera 

 of the Trematoporidse, although it is especially well developed in the 

 present form. 



Numerous thin sections of these several forms have been prepared 

 and the internal structure in each found to be identical. Moreover, 



1 



Fig. 188.— DrrropoEA colucttlata. Eichwald's FiGtrRES of 

 Tbematopoea colliculata. a and 6, fragment of zoarium, 



NATtTKAL SIZE, AND SUEFACE OF SAME, ENLARGED. "CALCAIEE A 

 OBTHOCERATITES," Reval, Esthonia. 



