3G0 Dr. E. Koehler on the Littoral Fauna of the 



at spring tides, and tliey open quite close to tlic entrance of 

 the preceding one. We penetrate through a fissure between 

 two rocks into a narrow passage, which gradually widens and 

 buries itself in the rock parallel to the direction of the large 

 cavern ; this passage constitutes the second cave, upon which 

 the two others open ; these are more spacious and go off at 

 right angles, to open upon the sea opposite the island of 

 Brechou. 



The last three caves have their walls completely covered 

 with equally numerous and varied animals, which, being only 

 laid dry at very long intervals, for a few hours every fortnight, 

 have attached themselves to the rocks and multiply rapidly, 

 presenting a vigour and a development which one does not 

 find in any other locality. There are, in the first place, Balani 

 {B. halanoides) which attain very considerable dimensions and 

 upon which are packed together Sponges, Simple and Com- 

 pound Ascidia, Bryozoa, and Hydraria, belonging to very 

 various species ; and the whole forms a thick living layer, 

 in which the abundance of forms, combined with the variation 

 of the brilliant colours, is well fitted to excite the admiration 

 of the naturalists who may visit this incomparably rich station. 



The Sponges are exceedingly abundant in the caves. 

 Bowerbank, who formerly visited them, records a great num- 

 ber of species ; but it is certain that the too lavish demands 

 of zoologists must have greatly impoverished this wonderful 

 station. Among the species which I have been able to 

 determine with certainty I will cite: — Grantia compressaf 

 Sycon tessellatum and S. ciliatum^ Leuconia nivea^ Grant, 

 LeucosoJema contorta, Bow., and Leucogypsia Oossei, Bow. 

 These Calcareous Sponges are very abundant, and the specimens 

 are always of large dimensions. Among the other Sponges I 

 will indicate: — Caminus osculosus, Gr., Geodia zetlandica^ 

 Johnst., Tethya lyncurium, Johnst., and T. Collingsii, Bow., 

 Microciona atrosan guinea^ Bow., Hymeniacidon mammeata^ 

 Bow., Halichondria 'panicea^ Johnst., Isodictya siinulans^ 

 Bow., and Baphyrus GrtJ/ifhsUy Bow., besides a great number 

 of undetermined specimens. 



The Actinia are represented by Actinia equina, the speci- 

 mens of which are remarkable for the differences of coloration 

 they present, varying from red to green, brown, yellowish, 

 and pure or yellowish white ; by Actinoloba dianthus, Ell., 

 and by several species of Sagartia, such as S. venusta, Gosse, 

 S. viduata, Miill., and 8. sphyrodeta, Gosse. Lastly, Cory- 

 nactis viridis is very abundant in the last two caves, and 

 presents several varieties, the most common of which corre- 



