627 



Insecta. 

 Cor et/ir a plumicornis Fabr. 

 Obgleich das Verzeichnis noch keinen Anspruch auf Vollständig- 

 keit machen kann, glaube ich dennoch schon aus demselben schließen 

 zu können, daß das Potamoplankton der Wolga dem der westeuro- 

 päischen Flüsse 1 im Ganzen sehr nahe steht. 



2. Carinoma Tremaphoros, a new Mesonemertean Species. 



By Caroline B. Thompson, B. S., Fellow in Zoology, University of Pennsylvania, 



Philadelphia, U. S. A. 

 (With 1 fig.) 



eingeg. 12. November 1900. 



While collecting at Wood's Hole, Mass., in July, 1900, one spe- 

 cimen of this Carinoma was taken. It is of especial interest, at it is the 

 first time this genus has been found in North America. In size and 

 shape it greatly resembles the heteronemertean Zygeupolia litoralis 

 Thompson, which is very abundant in this locality, but differs in its 

 flattened truncated head, paler color and absence of caudicle. 



Carinoma. 

 Generic characters according to Burger. Anterior end of body 

 not thickened but tapering. Mouth directly behind brain. A thick 

 inner circular muscle layer is present. Nephridia occur. 



Carinoma tremaphoros n. sp. 



External characters. Length about 12 cm, width 3 mm. Color: 

 head white, with opaque longitudinal striations, body buff, intestinal 

 diverticula and gonads showing as dark cross lines, tail end clear, 

 whitish, absence of intestinal diverticula very marked. Head flattened, 

 in life slightly constricted from body, anterior end rounded. Proboscis 

 pore subterminal, ventral. Body rounded anteriorly, posterior part 

 flattened and tapering. 



Internal anatomy from sections. Mouth small, directly behind 

 brain. Alimentary canal in three parts, anterior intestine, middle in- 

 testine with diverticula, posterior intestine (Enddarm) about 3 mm in 

 extent, no diverticula. Brain: little differentiation of dorsal and ven- 

 tral lobes, commissures long and stout, dorsal about one-fourth as 

 thick as ventral. 



1 O. Zacharias, Das Potamoplankton. (Zool.Anz. No. 550. 1898.) — O.Zim- 

 mer, Über thierisches Potamoplankton. (Biol. Centralbl. Bd. XVIII. 1898.) — S.Pro- 

 ■wazek, Das Potamoplankton der Moldau und Wotawa. (Verhandl. d. k.k. zool.-bot. 

 Gesellsch. in Wien. Bd. XLIX. 1899.) 



46* 



