[MATTHEW] STUDIES ON CAMBRIAN FAUNAS 109 



IIyolithellus micans, Bill, (pars) (PI. VI., figs, la to d). 



Hyolithellus micans, Bill, (pars), Nat. Hist. Soc. of New Brunswick, Bull, xviii., 

 p. 192, pi. ii., fig. la to d. 



The objects hereto referred appear to agree both in form, size and 

 association with the " long, slender cylindrical species " which Billings 

 has described under the above name. The only reason I have for doubt- 

 ing the relation to Billings's species is, that I have not been able to trace 

 these objects into tubes of so large a size as 2 or 2| lines. The latter is the 

 limit of size which he gives and which he says would require a length of 

 four or five inches for the shell. 



Size. — The longest of these objects which I have been able to break 

 from the matrix is 20 mm. with a diameter of scarcely 1 mm. reduced at 

 the small end to ^ mm. ; the full length would not be more than 40 mm. 

 (1| inches). 



Sculpture — Although these objects have a shining surface they are 

 HOC smooth but are minutely granulated and show no lines of growth 

 transverse to the tube, such as we find in most species of Orthotheca. 

 Those that occur with 0. bayonet have not as bright a surface as some 

 of the others. 



Mode of occurrence. — The peculiar attitude of these rods in the cal- 

 careous mud in which they are imbedded arrests attention. It is quite a 

 common thing to find two of these rods almost strictl}' parallel to each 

 other and quite commonly they occur in sheaf-like clusters, radiating at 

 a narrow angle from each other ; this would appear to indicate that they 

 are subsidiary organs belonging to some larger organism. Holm has 

 suggested that they are the spicules of sponges. Such an origin is pos- 

 sible, though I do not think it likely, for though these objects are rigidly 

 straight, or only slightly curved, yet examples filled with spar show that 

 the side walls were quite thin. Also, they have a diameter ten times that 

 of ordinary sponge spicules and twice the size of the groups of several 

 spicules, that form the mesh of Kuplectella. Thus while at first sight there 

 seems some probability in this view, especially when one observes the 

 smooth, shining surfaces of these tubes and their attitude in the lime- 

 stone ; it will not bear application, for against this explanation of their 

 origin is the fact that they are much larger than an}^ spicules of sponges. 

 Among the numerous forms figured in the Challenger Reports we can- 

 not pick out any that approach Hyolithellus in size ; the Tetractinellids 

 which appear to have the largest spicules still cannot show any that are 

 more than one-eighth of the diameter of Hyolithellus. The sponge- 

 spicules also usually have a narrow cavity within, while Hyolithellus has 

 a large one, the shell being thin. It is true that this genus as preserved 

 in the phosphate-bearing sandstones of the Protolenus Zone of the St. 



