138 ANNALS NEW YORE ACADEMY OF SCIENCES 



Description : Generally infundibuliform, branches more or less parallel, fre- 

 quently dividing, width of tissue 9-10 mm., cross-threads somewhat irregular, 

 of medium number ; open rectangular meshes ; thecse 15 to 17, projecting, of 

 medium size. 



Notes: Slight changes of the characters are fully shown on the diagram, 

 Plate XX. Greatest length observed about 200 mm., width 190 mm. ; approxi- 

 mately 2 x 150 branches. 



The variation of the number of thecse is marked, 16 being present on 

 the American examples, hut only 10-15 in 10 mm. on the European ex- 

 amples. This fails to be of general value, as G. E. Matthew has pointed 

 out, since the figures of Brogger (5) and Tullberg (8) also exhibited 16 

 thecae and Westergard states recently a usual number of 15-16 thecse on 

 the Swedish examples ((4), p. 58). When comparing the form, col- 

 lected by Prof. A. W. Grabau from Skane (region of Fogelsang), with 

 the American specimens, a more delicate character of the whole tissue of 

 the European type is apparently the one observable difference on which 

 a separation of var. acadica Matth. and "forma typica" of the Swedish 

 authors can be based. 



Var. conferta Linrs (ms.) 11 

 Apotypes : 



(6) 1860. Goppert, pi. 36, fig. 11, 4. 



(9) 1861. Salter, Geol. Survey Gr. Brit., Mem. 3, pi. 4, fig. 1. 



1881. Salter, Geol. Survey Gr. Brit., sec. ed., p. 535, pi. 41, figs. 1, la, 1&. 



(8) 1882. Tullberg, p. 20, pi. 3, fig. 3 (1,2?). 



(4) 1909. Westergard, pi. 3, fig. 7. 



Description: Characterized by Brogger ( (5), p. 36) as having very fine and 

 close network and cross-threads of the same kind. 



Matthew 12 added "commonly vasiform, cross-threads more frequent than in 

 acadica (5-7). 15-17 thecse are usually met with in 10 mm." 



I have observed even 18 on a typical specimen ; young specimens often 

 show only 14-15 thecse. The rigid aspect of the branches and their 

 regular branching, which commonly takes place in the same level, seem 

 rather important additional features. Here, too, a little more delicate 

 structure of the whole tissue distinguishes the Swedish specimens,, so that 

 Westergard found 13 branches in 10 mm. of width, while 8-10 branches 

 may be usually numbered on the American variety. The largest ob- 

 served colony measures 22 mm. in width, occupied by 19 branches, and 

 82 mm- in length. 



"Brogger (5) furnished as long ago as 1882 an undoubted description of this form, 

 while Pocta created his species "conferta" not earlier than 1894 (Systeme silurien, 

 Bryozoaires, etc., Vol. VIII, t. ler, p. 194). The last ought to be renamed, if this is 

 necessary at all. 



12 Loc. cit. 



