464 Mr. W. Lonsdale on the Genus Lithostrotion. 



lines of the investing layer. The Nemaphyllum of Prof. M'Coy 

 needs no remarks under this head, the corallites being described 

 as inseparable {op. cit. p. 15). The author is unable from 

 want of means to extend this portion of the inquiry into the 

 characters of English basaltiform corals ; but the Russian fossil 

 to which he applied the term Stylastrea inconferta (Geol. Russia, 

 App. A. p. 621-622) presented exteriors resembling those just 

 mentioned ; though he is not aware that Styl. irregularis (M'Coy, 

 op. cit. p. 9) has similar minor structures. Lastly, as respects 

 this character, Mr. Dana states, that his Columnaria break into 

 columns, without however mentioning the exterior condition of 

 the parted corallites. A comparison of the limited materials thus 

 brought under the reader's attention will afford the following 

 points of difference as respects the connexion in branched and 

 massive or asteriform species of Lithostrotion (Archives). In the 

 former, juxtaposition, as before stated, is an occasional condition, 

 and where a junction takes place, whether by processes or con- 

 tact, a separation produces a fractured surface : on the contrary, 

 in the massive species examined the corallites were uniformly 

 contiguous ; and when parted, they did not exhibit a disrupted, 

 but a perfect exterior, as well as the minute lines of increment; 

 while in specimens which had lost the coral matter during mine- 

 ralization, or had been otherwise deprived of it, there was an 

 equal absence of fracture — the exposed facets in the one case dis- 

 playing casts of the original structures; and in the other, a 

 smooth surface with an unbroken reticulation. 



The precise mode in which additional corallites were produced 

 in Lithodendi'd or branched species of Lithostrotion, the author 

 believes, has not been described ; and he is able to give but im- 

 perfect notices of early states in only two, referable he conceives 

 to Lithod. irregulare and Z. sexdecimale (Phillips). Polished trans- 

 verse sections of the former afforded two examples of incipient 

 branches. One of them, and probably the younger, presented a 

 lateral semicircular projection, about half the diameter of the 

 parent stem. The straight side, or that in contact with the old 

 corallite, was situated within the substance of the latter, but was 

 separated from it by a strong partition-wall — a fine, more opake 

 line defining the boundary beyond the two bodies; while the 

 curved portion protruded markedly beyond the periphery of the 

 old branch, and had its own white wall. The minute area thus 

 circumscribed was occupied principally by lamelke-like plates, 

 two or three of which ranged directly across it, or from the 

 straight to the curved side ; but the others had a more irregular 

 outline, and were forked or connected by transverse laminse. 

 There was however no convergence to a centre ; nor any medial 

 point indicative of an axis ; the plates bearing more the semblance 



