468 On a new Genus of Palceozoic Fossils. 



only other recent forms to which we can find any likeness 

 with Ascodictyon are some of the Sertularians (e. g. S.pumila)^ 

 there being a decided resemblance between the thread-like 

 fibres which creep along the foreign bodies to which these 

 organisms are attached, and which connect the polyjDiferous 

 shoots, and the netted stolons of ^. radians and A. stellatum. 

 In other respects, however, the structure of Ascodictyon is by 

 no means Hydrozoal. Upon the whole, therefore, we can 

 only leave the question as to the systematic position of Asco- 

 dictyon in the meanwhile undecided, in the hope that future 

 researches may enable us to find a definite niche in the system 

 for these interesting fossils. 



We are much indebted to our friend Mr. James Bennie for 

 the loan of his beautiful specimen of A. radians. 



EXPLANATION OF PLATE XIX. 



Fig, 1. Portion of a colony of Ascodictyon stellatmn, Nich, & Eth., Jun., 

 growing upon the hinge-area of Cyrtina hamiltonensis, Hall, 

 magnified 10 diameters. 



Fig. 2. A single group or rosette of the same, enlarged 20 diameters. 

 The connexion of the vesicles with one another and with the 

 basal stolons is here hidden by adherent matrix. 



Fig. 3. Portion of the creeping stolon of a colony of the same, highly 

 magnified, showing the single row of pores along the free 

 face. 



Fig. 4. Two rosettes of the same species, enlarged 2-5 diameters. The 

 lower rosette is complete ; but one of the vesicles is partially 

 fractured, shomng its internal canity, and another has its ex- 

 tremity directly prolonged into a stolon. 



Fig. 5. A single rosette of the same, enlarged 30 diameters. In the 

 centre of the rosette is a central chamber (?) ; and several of the 

 vesicles have their internal cavities exposed by fracture. 



Fig. 6. Four detached young (?) vesicles of the same, growing on the 

 binge-area of Cyrtina hamiltonensis, Hall, greatly enlarged. 



Fig. 7. Portion of a colony oi Ascodictyon fusiforyne, Nich. & Eth., Jun., 

 growing upon the mesial fold of Spin/era mncronata, Conrad, 

 enlarged 15 diameters. 



Fig. 8. A single cellule of the same, enlarged 30 diameters. 



Fig. D. Fragment of the stem of a Crinoid, to which is attached a colony 

 of Ascodictyon radians, Nich. & Eth., Jun., of the natural 

 size. 



Fig. 10. A single rosette of the same, magnified 30 diameters. At a a 

 stolon given out by the extremity of one of the vesicles is seen 

 to connect itself directly with the corresponding extremity of a 

 vesicle belonging to another rosette. 



Fig. 11. A single vesicle of .4. ra^/iViHS, magnified to show the central line 

 of pores. 



