712 



Report of the State Geologist. 



Canada creek, which yields specimens of this Co mil aria not larger than .5 

 mm. in length, and which, therefore, enables the author to furnish some 

 further details relating to the development of the shell of this interesting 

 animal (cf. PI. IV). The minute, oval, carbonaceous bodies cover some of 

 the layers in astonishing multitudes. 



While the great majority of the tiny fossils are found promiscuously 

 scattered over the slabs, some of the latter, otherwise pool- in such detached 

 specimens, bear linear carbonaceous films, with outlines so straight and w ell 

 defined as to make it improbable that the film should be the result of an 

 accidental drifting together of shells. One of these bodies has been reproduced 

 in figure 1, Plate IV, on account of the distinctness with w hich it shows its 

 composition of young shells of Conularia. There are others of more regular 

 outline, the most complete of which attains a length of 31 mm. and tapers 

 regularly from a width of 5 mm. at one end to 4 mm. at the other. This film 

 consists of minute shells of Conularia, which become especially distinct at 

 both of its ends, where it is more or less lacerated. The shells observable 

 in these films range in length from .5 mm. to 2 mm. A few specimens 

 (cf. fig. 2) have been collected, which indicate that the shells were sometimes 

 regularly arranged and attached to some central body, which, in the original 

 of this figure, is not preserved. Whether these probably originally cylin- 

 drical aggregates of spawn of Conularia are brought about by the crowded 

 fixation of young individuals around extraneous bodies, as <-. </., fragments of 

 seaweed, which are not preserved, or whether it is a case of brood-protection, 

 has not been ascertained with the material thus far collected. 



There can. however, be no doubt that the animals, in the infantile 

 condition which comes under observation here, were already seeking attach- 

 ment to other bodies, in spite of their usual irregularly scattered 

 occurrence on the slabs, which might suggest a swimming habit. This 

 is clearly shown in very youthful stages found attached to little cones 

 (probably belonging to a Monticulvpora), which project from the slabs 

 (cf. fig. 3), and above all by the possession of the organ of fixation, namely, 

 the basal appendage. 



There have been no shells found which did not reach a length of .5 mm., 

 while fossils between .5 mm. and 1 mm, are quite common. This smallest 

 stage obtainable (cf. figs. 4 to 7. PI. IV), is characterized by the presence, and 

 relatively large size of the basal cup, w hich attains half the size of the entire 

 shell : by the apparent greater breadth and by the curved outline of the 

 living chamber, which often approaches a circular shape. 



