A Fossil Alga. 15 



in associating Mr. Carruthers' name: Caulerpa Carruthersii, n. sp.: 

 frondibus erectis, annulato-constrictis, simplicibus, ramentaceis, ramentis 

 verticillatis, clavato-obovatis, strictura conspicua a rachide sejunctis, quasi 

 articulatis ; surculus nondum inventus. 



The species of Caulerpa at present existing are mostly tropical, a few 

 of them reaching as far north as the Mediterranean and as far south as 

 the Cape of Good Hope. We may say approximately that they are 

 confined within the fortieth* parallels of north and south latitude, but 

 occur more plentifully as we reach the equator from either hand. If we 

 may judge by the marine fauna of the Kimmeridge clay, it is such as would 

 favour the view of the climate being suitable to the occurrence of Caulerpa. 



Though I do not venture to claim for this determination the cer- 

 tainty which would be yielded by tissues preserved in a state fit for 

 microscopic examination, yet I would point out that we are dealing 

 here with no mere flattened impression, but with a cast exhibiting in 

 the round all the details of external conformation in great perfection, 

 that these characters agree closely with living representatives, that the 

 deposit is a marine one, and the conditions of climate fitting. Taking 

 all this evidence pointing in one direction, I would therefore venture to 

 urge the recognition of my contention that we have here evidence of 

 the existence of an Alga in the secondary rocks of far greater weight than 

 has hitherto been brought forward. The fact that it, like the other fossil 

 Algae, certainly known to us as such (except the diatoms and Litho^ 

 thamniori), is a siphoneous Alga may have a certain significance. Owing 

 to the plentiful lack of material, I do not choose to draw any inference 

 from such facts, though others may have a taste for the pastime. 



GEORGE MURRAY. 



EXPLANATION OF PLATES. 

 PLATE IV. 



Fig. i. Caulerpa Carruthersii, G. Murr. Nat. size. a. Section near apex. 

 Fig. 2. a. b. c. Sections seen in cross fracture. Nat. size. 

 Fig. 3. Ideal figure of C. Carruthersii. 



PLATE V. 



Fig. i. Specimen of C. Carruthersii in Museum of Practical Geology, Jermyn 

 Street. Nat. size. 



Fig. 2. a. Caulerpa cactoides Ag. var. gracilis. Nat. size. b. Cross section of 

 C. cactoides ( x 15 ). c. Longit. section ( x 15), after figures by the author in Linn. Soc. 

 Trans. ot. y vol. iii., pt. 4, plate LII. 



* They come slightly to the north of 40 in the Mediterranean. 



