310 Henry Woodward — Fossil Balanus from Mekran Coast. 



other a group often very well preserved individuals clustered together^ 

 of which a figure is given in the text below (Fig. 2). They have 

 been most successfully developed from the hard concretionary 

 matrix by Mr. Richard Hall, the Museum Formatori, and the only 

 regret is that none of the opercular valves have been preserved, or, 

 I may say, have not been exposed to view, during the process of 

 removing the matrix. (In specimens of Balanus concavus and other 

 species from the Coralline Crag of Suffolk, I have frequently 

 recovered the perfect set of opercular valves from the interior of 

 the body-chamber, and, but for the hardness of the matrix, they 

 might almost certainly be found within the interior of these fossil 

 ' acorn shells ' of the Mekran Coast also.) 



Fig. 2. — Group of ten individual Balaui developed out of the interior of a con- 

 cretionary nodule from the cliffs on the seashore, Ormara Headland, Meki-an 

 Coast. Referred to Balanus tintinnabulum, Linn., var. coccopoma, Darwin. 



The orifice of the shell (if complete) would have been enclosed 

 by these moveable valves, i.e. by a pair of tergal and two scutal 

 valves, upon the characters of which the species could at once have 

 been determined. We have, then, only the shell-walls, composed 

 of a carina, a rostrum, two rostro-lateral and two carino-lateral 

 compartments, which, with their interlocking radii and ala3, enclose 

 the body-chamber on every side, the lower surface being protected 

 by the hasis (not visible), which varies greatly in different genera, 

 as indeed do also the walls of the shell itself. 



After a careful comparison of the specimen with Charles Darwin's 

 beautiful plates and descriptions of the sessile forms of Cirripedia 

 (Balanidfe, Eay Society, 1854), I am led to conclude that tlie 

 nearest species to our fossil is Balanus tintinnabulum, Linn., and of 

 its many varieties probably Darwin's (var. 7) coccopoma best 

 represents it, its form being globulo-conical, orifice small, walls 

 rounded, generally smooth, thick (colour x). Some of the com- 

 partments show, in addition to lines of growth, fine wavy raised 

 plicae or parallel stride, but for the most part lines of growth are 

 alone visible. 



