Miscellaneous, 433 



and similar to the ordinary cicatriculse, or is it tlie result of the 

 early fusion of two primarily distinct eicatriculae or germs ? Since 

 M. Balbiani has shown how the germ is formed in the ovule, we may 

 consider whether certain ovules may not contain a cicatricula appa- 

 rently simple, but formed by the fusion of two originally distinct 

 germs. And the coexistence of two germs within a single ovule is 

 proved by the coexistence of two separate cicatriculse upon the same 

 vitellus. 



The author has recently observed an egg presenting a very singu- 

 lar arrangement, but which is explained by a combination of the two 

 cases above described. In this there were two transparent areas 

 upon a single blastoderm and in a single vascular area, the latter of 

 a very abnormal form. One of the transparent areas was normal, 

 and presented a normal embryo ; the other, of an irregular form, 

 presented two embryos, one normal, the other abnormal. This fact, 

 although apparently very complex, may be very simply explained by 

 the coexistence upon the same vitellus of two distinct cicatriculae, one 

 normal, the other formed by the fusion of two germs, and by the 

 production of a single blastoderm from these cicatriculae during in- 

 cubation. — Comptes Rendus, March 20, 1865, p. 562. 



On two Starfishes from Costa Rica. By E. von Martens. 



On the 16th January Dr. E. von Martens communicated to the 

 Academy of Sciences at Berlin a description of two species of Star- 

 fishes from Costa Rica. The first of these is the Oreaster armatuSy 

 Gray, which is described as follows : — 



I . Oreaster armatus, Gray, sp. 



Body pentagonal, with strongly incurved sides ; proportion of the 

 radius of the disk to that of the arms as 1 to 1^ nearly. Dorsal sur- 

 face but little elevated. Ambulacral papillae in two rows ; on the 

 inner plates three and more, rarely two, placed close together upon 

 each plate ; on each of the outer plates one larger papilla. The plates 

 of the ventral surface are thickly set with globular granules, and 

 bear on the middle of each a large cylindrical tubercle which is ob- 

 tuse at the apex. The lower marginal plates belong entirely to the 

 ventral surface : they are thickly set with globular granules, and bear 

 in the middle of each a larger, conical, moderately acute spine, which 

 is villous, like satin, and the narrowed flat base of which is sur- 

 rounded, as by a wall, with the granules of the marginal plate itself. 

 There are seventeen inferior marginal plates between the apices of 

 each pair of arms ; they are all nearly square. The superior mar- 

 ginal plates, which alone form the margin, are twice as high as their 

 breadth in the middle of the space between two arm-tips ; towards 

 the latter they become broader in proportion, and finally nearly 

 square. Their number between each pair of arm-tips is fourteen. 

 They are beset with granules, in the same manner as the inferior 

 marginal plates, and bear a precisely similar spine in their middle ; 

 many of them, however, are destitute of the spine and even of every 



Ann. ^Maff.N. Hist. Ser. 3. Vol.xv. 29 



