MINUTE STRUCTmE OF STROMATOPORA AND ITS ALLIES. 235 



posed of a series of short, discontinuous, fusiform, calcareous 

 columns (a), which are about half a line in width, and are placed 

 about half a line to a line apart. The spaces between these 

 columns are occupied by curved calcareous lamellae (&), which 

 form a series of comparatively large lenticular vesicles (c). The 

 upper surface is formed by the upper surfaces of these calcareous 

 lamellae, and by the prominently protruded free ends of the 

 columns. The columns are wholly solid and imperforate, as are 

 the lamellae of the vesicular tissue. The vesicles of the latter, 

 therefore, appear to be entirely destitute of any intercommuni- 

 cation, and we have failed to detect any openings or ^^ores of any 

 kind on the upper surface. The lower surface is likewise imper- 

 forate, and is covered by a concentrically striated calcareous 

 membrane or "epitheca," which envelops all the inferior surface, 

 except the comparatively small peduncle by which the colony is 

 attached to foreign bodies. 



That there is some resemblance between Lahechia and some of 

 the coarsely tuberculated species of Stromatojpora is undeniable ; 

 but it appears to us to be a superficial likeness, and we are not 

 prepared at present to offer a decided opinion as to the affinities 

 of the former. That LahecMa has also a general resemblance to 

 the crusts of Hydractinia is also undeniable, especially now that 

 Mr. Carter has described calcareous species of the latter genus 

 (Ann. & Mag. Nat. Hist. ser. 4, vol. xix. 1877); but there are 

 the following very important points to notice in this connexion. 

 The colonies of Lahecliia are not incrusting^ as are those of Hy- 

 dractinia, but form expansions, resembling those of many corals, 

 attached to a foreign body at one point, but having the greater 

 portion of the inferior surface free and covered by a concentri- 

 cally striated "epitheca." The columns of are invari- 

 ably solid throughout, whereas the spines of Hydractinia are more 

 or less reticulated basally, or traversed by a central canal. Lastly, 

 the upper surface of Lahechia has not yet been shown to jDresent 

 any apertures or crypts, such as may be supposed to have given 

 exit to zooids of any description. 



Eecently Mr. Carter has thrown out the suggestion, and has 

 strongly supported the view, that Stromatopora is truly very 

 closely related to Hydractinia. "We have very carefully studied 

 the two memoirs which Mr. Carter has published bearing upon 

 this subject (see Ann. & Mag. Nat. Hist. ser. 4, vol. xix. p. 41, 

 1877, and ibid. ser. 4, vol. xi. p. 1, 1878), and we have also spo- 



LINX. JOXJR'N^. — ZOOLOGY, VOL. XIY. ]7 



