170 BULLETIN 77, UNITED STATES NATIONAL MUSEUM. 



As indicated under the generic remarks, C. tenella is based upon a 

 very common BorkhoLm limestone species quite similar to Hall's 

 Retepora angulata. This similarity is so great that had the Russian 

 specimens been derived from the American Clinton deposits holding 

 Hall's species they would probably have been identified as the 

 same. However, untU a detailed study of aU the species of Ghas- 

 matopora and related genera has been made, I prefer to regard C. 

 tenella as distinct, recognizing, as did Eichwald, this great similarity. 

 The fenestrules of C. tenella are quite regularly 

 angular in outline and average 2.5 mm. in length 

 by 1.0 mm. in width. Eichwald's figure (fig. 85) 

 shows this angularity and also indicates the number 

 of zooecial apertures. The noncelluliferous side is 

 Fig. 85.-CEASMATO- longitudinally striated. 

 poEA TENELLA. OccuTvence. — Eichwald registers this species from 



Ot^'T T TTT TPETt. OTIS 



FACE ENLARGED, thc Iskud of Dago, and from Baltischport and 

 "Calcaiee a oe- Spitham, Esthonia. Specimens are abundant in the 

 baltischpoet, es- Borkholm limestone (F2) at Borkholm, Esthonia 

 THONiA. (AFTER (Cat. No . 57263, U.S.N .M.) . 

 icHWALD. ^^^ collections of the British Museum contain 



specimens and thin sections from the Borkholm limestone, Borkholm. 



J 



CHASMATOPORA RETICULATA (Hall). 

 Text fig. 86. 



Intricaria? reticulata Hall, Nat. Hist. New York, Pal., vol. 1, 1847, p. 77, pi. 26, 



figs. 8 a-c. 

 Subretepora reticulata Miller, North Amer. Geol. and Pal., 1889, p. 326, fig. 524. 

 Phylloporina reticulata Ulrich, Geol. Surv. Illinois, vol. 8, 1890, pp. 332, 639, pi. 



53, figs. 2, 2 a; Geol. and Nat. Hist. Surv. Minnesota, vol. 8, pt. 1, 1893, p. 



210, pi. 4, figs. 8-15. 



A number of specimens indistinguishable from the types of this 

 interesting bryozoan have been found in the Wassalem beds at 

 Uxnorm where they are associated with numerous other American 

 Black Eiver species. The following description and text figure, 

 copied from Ulrich, will serve equally for the recognition of the 

 Russian specimens : 



Specimens as seen, consisting of small, flat or undulating, reticulate expansions, 

 being in each case evidently fragments of a depressed, funnel-shaped zoarium, prob- 

 ably not exceeding 5 cm. in diameter. Branches rounded in section, 0.2 to 0.3 mm. 

 in diameter, inosculating at unusually frequent and regular intervals. Fenestrules 

 somewhat elongate, about as wide as the branches, subrhomboidal in shape in the 

 more regularly constructed fragments; their number in a given space is fahly constant, 

 the extremes noticed in 1 cm. being ten and twelve. Reverse of branches convex, 

 finely striated lengthwise. 



