171 



4. A new species of Semper's larva from the Galapagos Islands. 



By Harold Heath, Leland Stanford Jr. University, California, U. S. A. 

 (AVith 1 [4] Figs.) 



eingeg. 1. März 1906. 



In 1867 Semper^ described a peculiar type of pelagic larva cap- 

 tured in tropical waters by Prof. Behn in Kiel and subsequently by 

 Semper himself in the neighborhood of the Cape of Good Hope, the 

 Mozambique Channel and off the coast of Java. Upwards of a quarter 

 of a century later van Beneden^ described a second species taken in 

 the Altantic close to the Cape Verde Islands. Recently this same author ^ 

 has proposed the generic name ZoanthcUa to include these organisms 

 commonly known as Semper's larvae, designating the one described by 

 Semper Z. semper i and the other Z. henseni. The characters of the 

 genus are thus described (free translation): »Pelagic larvae attaining a 

 length of 13 mm. Body elongated, provided in one species with a flagel- 

 late plate and in the other with a vibratile fringe, extending in both 

 parallel to the axis of the body along the anterior median line. Twelve 

 septa, of which six are macrosepta and six microsepta, disposed as in the 

 Zoanthariae (microtype of Erdmann). Aboral pore present or absent.« 



Recently another species of this proposed genus, which I have 

 called Zoautheila galapagoensis ^ came to light in a vial of pelagic cope- 

 pods taken by Messrs. Snodgrass and Heller in the neighborhood of 

 the Galapagos Ids. There was but a single specimen, 6 mm in length, and 

 where an external delicate coat, apparently a mucous secretion had been 

 removed, the epithelium appeared light chocolate brown in color ob- 

 scurely flecked with small, lighter almost grayish patches. It is possible 

 however that this effect may be the result of age or some reagent. 



The body is spindle shaped with the mouth at the extremity of the 

 more slender half. In common with other members of the genus no sign 

 of tentacles exists: and a heavy ciliated fringe extends from the mouth 

 along the anterior median line to a point about 1,75 mm from the aboral 

 pole. As Semper clearly shows in Z. semperi this band pursues a 

 slightly spiral course, scarcely evident in fact with the present species. 

 The anterior surface is distinctly flattened and in the neighborhood of 

 the mouth is slightly grooved, the cilia springing from the bottom of the 



1 Über einige tropische Larvenfoi-men. Zeischr. f. wiss. Zool. Bd. XVII. S. 407 

 -420. 



- Les Anthozaires pélagiques recueillis par le professeur Hens en, dans son 

 expédition du Plankton- I. Une larve voisine de la larva de Semper. Bull, de T Acad. 

 roy. de Belg. 3. Ser. T. 3. p. 55—99. Same article in Arch, de Biol. T. 10. p. 485—521. 



3 Les Anthozaires de la »Plankton-Expedition«. Res. de la Plankton-Exp. d. 

 Humboldt-Stiftung. Vol. II. 1898. 



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