500 



LONSDALE ON MIOCENE CORALS FROM N. AMERICA. 



Astrea hirto-lamellata. 

 Near the point indicated 

 by the letter (a) is an im- 

 perfect star, due apparently 

 to a subdivisional process 

 in the fully developed star 

 next to it. 



[Natural Size.] c 1 



The fossil referred doubtfully to M. 

 Michelin's species consisted of a series of 

 young stars attached to a Balanus, and 

 therefore did not exhibit an equivalent 

 state of development to the specimen 

 figured by that authority ; but the gene- 

 ral resemblance between the corals was 

 too great to justify the proposing a distinct 

 specific name. 



The American fossil presented appa- 

 rently only one condition of growth, the 

 terminal cups penetrating to the thin base- 

 layer which coated the surface of the Ba- 

 lanus, and there was scarcely a trace of 

 interstitial laminae ; the narrow lamellae 

 were also very indistinct on the lower 

 side of the walls. The specimen never- 

 theless displayed different degrees of de- 

 velopment, in consequence of the production laterally of additional 

 stars. In the more mature stage the walls had a relatively consi- 

 derable elevation, and the broad lamellae a great regularity of 

 character : there was, moreover, among these stars an important 

 instance of a young one, due, it was believed, to a subdivisional 

 process. In the less mature stage, the walls, though equally sharp 

 on the upper edge, had much less height, and the broader lamellae 

 were unequally developed. The example of what was considered 

 a subdivided star — a characteristic of Ehrenberg's restricted genus 

 — is given near the letter (a) in the wood-cut, and it exhibits 

 what are believed to be satisfactory proofs of its origin ; the wall 

 on one side being regularly angular, and lined with alternately 

 broad and rudimentary lamellae uniformly developed, while on the 

 opposite side the wall is arched, and there are only two irregular 

 lamelhe-plates. 



Locality. — Williamsburg. 



B. Polyp aria Bryozoa. 

 4. Heteropora ? tortilis. (Sp. n.) 



Branched ; branches dichotomous, thick, short ; tubes long, cylindrical or 

 slightly compressed, sometimes in contact, sometimes slightly separated by in- 

 termediate animal secretions, divergence great ; walls thin, minutely punctured, 

 not separable mechanically ; no transverse diaphragms ; larger tubular openings 

 round or slightly angular, edges sharp, no regular arrangement ; smaller open- 

 ings round or angular, often very numerous, occasionally few in number ; addi- 

 tional tubes produced partly in the axis, partly in the lateral portions of the 

 branches. 



The genus Heteropora *, established by M. cle Blainville on 



* Ehrenberg's genus Heteropora (Beitrage, &c. 1831 — -1834. and Berlin 

 Trans. 1832.), founded on a subdivision of Lamarck's Madrepores, was probably 

 proposed about the same time as De Blainville's (Man. d'Actinol. 1830 — 1834.), 

 but it does not appear to have been adopted. 



