No. 9. — Reports on the Scientific Results of the Expedition to 

 the Eastern Tropical Pacific^ in charge of Alexander Agassiz, 

 by the U. S. Fish Commission Steamer " Albatross " from 

 October, 1904-, to March, 1905, Lieut. Commander L. M. 

 Garrett, U. S, N., Commanding. 



III. 



Craspedotella, a new genus of the Cystoflagellata, an 

 example of convergence. By Charles Atwood Kofoid. 



In the plankton obtained by the Eastern Pacific Expedition of the 

 U. S. Fish Commission Steamer "Albatross" in 1904-5 there occurred 

 a Cystoflagellate belonging to the Leptodiscidae which is of unusual 

 interest not only because of its relationships, but especially on account 

 of its striking resemblance in form to a craspedote medusa. The same 

 organism subsequently appeared in the plankton collected in June at 

 the San Diego Marine Biological Station of the University of Califor- 

 nia. It was first taken in the mid-Pacific at Albatross Sta. 4730, about 

 15° 7' S., 117° 1'.2 W., midway between the Galapagos Islands and 

 Manga Reva. This fact, together with its occurrence oif the coast of 

 Southern California, is indicative of a wide distribution in warm- 

 temperate and tropical seas. 



This organism is minute in comparison with Leptodiscus medvsoides 

 R. Hertwig (0.6-1.5 mm.) or Noctiluca miliaris Suriray (0.3-1.25 mm.), 

 being only 0.15-0.18 mm. in diameter. Its form is campanulate, with 

 a very well-defined horizontal velum. A large plasma mass is sym- 

 metrically pendent from the centre of the bell, whose cavity forms about 

 two thirds of the volume of the organism. In polar view its outline is 

 circular, and the orifice bounded by the velum is also of the same form. 

 It is thus distinctly similar to a craspedote medusa in its form, resem- 

 bling somewhat Laodirea cellularia A. Agassiz. The resemblance is 

 further enhanced by the circlets of refractive granules found in the 

 salient margins of the oblique band, while radial plasma strands in this 

 band and in the velum suggest a muscular activity of the bell and 

 resulting locomotion similar to that of a medusa. Its resemblance to 



VOL. XLVI. — NO. 9 



