338 PROCEEDINGS OF THE 



smallest degree, either protective or defensive in design or 

 character. 



That the fragments of crinoids were more suitable than other 

 marine exuviae for parasitic constructions is unlikely; but they 

 may, probably, have been more abundant in the oceans of the 

 Carboniferous eras. These structures are apt to puzzle young 

 palaeontologists, for long observation is often necessary to interpret 

 what is oftenest seen. Nothing is more common, for example, 

 than the basement portion of crinoids, but it may be long before 

 connection of parts establish their nature. 



The same thing may take place with regard to the basement 

 or root portions of the polyzoa, often found on crinoids without 

 stem or frond. A few specimens of this order may be described 

 to exemplify the fact : 



1. A fragment of encrinite, fully half an inch long and 2 lines 

 diameter, has evidently an adventitious structure on one side, of 

 calcareous matter, and irregularly rounded in form; thin, but 

 with strong strengthening bands, on which appear fine striations 

 and several raised small round apertures. The construction, in 

 this instance, may be mistaken for the work of Seijoula. 



2. Another fragment, similar in most respects, but less perfectly 

 marked. 



3. A fragment of encrinite, with the tumid or diseased aspect, 

 has on one end a very distinct structure, identical in character 

 with the two previous specimens; but, in addition, the frond of a 

 FenesteUa is in connection, bearing strong evidence of having been 

 based and supported on and by the structure. Thus a puzzle of 

 long duration was solved. This specimen has the characteristic 

 perforation on one side, with other characteristics common in 

 injured crinoids; but somewhat strangely, the hole in the side 

 is occupied with the root and part of the stem of another polyzoon. 

 This is a most interesting and instructive specimen. 



4. Is a small bit of encrinite, with a comparatively large 

 tubercle of adventitious calcareous substance, which seems set in, 

 rather than on, the fragment, it being contorted somewhat, and 

 interrupted in development. This is seen distinctly in the lower 

 ossicle, as well as in the depression of the stem. This structure 

 must have been made during the life of the animal. The tubercle, 

 although without characteristic striations, seems, in structure, to 

 be the same as those described as roots of polyzoa. The genius 



