LOWER CAMBRIAN. 41 



the contained coenosarc continues to elongate itself until it ruptures the 

 delicate pellicle of chitine which closes the extremity of the ramulus. It 

 then extends itself, quite naked, into the surrounding water, and a constric- 

 tion takes place at some distance below its distal extremity in the parts 

 still covered by the chitinous perisarc. The constriction rapidly deepens 

 and ultimately cuts off a piece, which slips entirely out of the perisarcal 

 tube and becomes a free zooid, while the surface of disseveration soon heals 

 over and the axial cavity of the free frustule becomes as completely closed 

 as at the opposite end. 



In tracing the further history of the frustule, it was found that this 

 never directly develops a mouth or becomes transformed into a hydranth. 

 After a time a bud springs from its side, and it is from this bud alone that 

 the first hydranth of the new colony is developed. 1 



I have mentioned this type of fission on account of the rarity of repro- 

 duction by that process among the Hydroida. It departs quite widely from 

 the mode of fission described by Dr. Lang, and is not, I think, comparable 

 with that which takes place in Laotira cambria. 



FOSSIL MEDUSAE OF THE LOWER CAMBRIAN TEREANE OF EASTERN 



NEW YORK. 



The manner of occurrence and the mode of preservation of the one 

 species found at this horizon in America are stated in the discussion of the 

 relations of the Middle Cambrian fossil medusae to those of the Lower 

 Cambrian (p. 8) and in the following description of the species: 



Genus DACTYLOIDITES Hall. 



Dacttloidites asteroides Fitch. 



Pis. XXIV to XXVIII. 



Buthotrephis ? asteroides Fitch, 1850. Trans. New York State Agric. Soc, Vol. IX, 



for 1849, p. 863. 

 Dactyloidites bulbosus Hall, 1886. Thirty-ninth Ann. Rept. Trustees State Mus. Nat. 



Hist. New York, for 1885, p. 160; pi. 11, figs. 1, 2. 

 Dactyloidites asteroides Walcott, 1891. Tenth Ann. Rept. TJ. S. Geol. Survey, Part I, 



p. 605; fig. 61, p. 606; PI. LVII; PI. LVIII, figs. 1, la. 



The description and figure of this species by Dr. Asa Fitch are very 

 incomplete, but they are sufficient for the identification of the species in 



'Loc. cit., pp. 152, 153. 



