vm. D. 4 Wharton: Some Philippine Thalassemse 261 



On account of these characters, I propose to erect the genus 

 Ikeda with the following characteristics: 



Genus IKEDA novum 



Nephridia, indefinite in number, not arranged in pairs, and 

 provided with terminal funnels; longitudinal muscle of the der- 

 mal musculature lying on the outside of the circular and oblique 

 layers. This genus at the present time includes only the type 

 species, Ikeda tsenoides (Ikeda). 



On account of the scattered condition of the literature on 

 Thalassema, it has seemed advisable to give as nearly as possible 

 a complete bibliography of each species of Thalassema, and this 

 has been added at the end of the key to the genera Thalassema 

 and Ikeda which follows. 



Key to the genera Thalassema and Ikeda. 



o'. Gephyrea in which the nephridia are arranged in pairs. The longitudi- 

 nal muscle of the dermal muscle layer lies between the circular and 

 oblique layers. No posterior ring of setae.. Genus Thalassema Gaertner. 

 6\ Forms possessing 1 pair of nephridia. 

 c'. Longitudinal muscles continuous. 



d'. Nephridia without spirally coiled internal openings. 



e\ Proboscis about as long as the body and forming a tube just 

 before it joins the body. Anal trees very short and trans- 

 parent like glass T. diaphanes Sluiter. 



e^ Proboscis small. Anal trees of moderate size with irregular 



branches T. faex Selenka. 



e'. Proboscis less than half the length of body. Anal trees bear 

 large funnels situated close together on long stalks. 



T. owstoni Ikeda. 

 e*. Proboscis about h length of body. Anal trees as long as body 



with few short, ciliated funnels T. fuscum Ikeda. 



e°. Proboscis trilobed at tip. Anal trees short and sac-like. 



T. gigas Max Miiller. 



e'. Proboscis short. Anal trees short, with funnels on short stalks. 



Anal trees attached to body by means of muscular filaments. 



T. arcassonensis Cuenot. 

 cf. Nephridia with spirally coiled internal openings. 



e\ Proboscis bilobed. Anal trees branched with funnels at tips of 



branches T. lankesteri Herdman. 



c^ Longitudinal muscles forming bundles which may or may not be 

 separated. 

 d\ Nephridia with spirally coiled internal openings. 



e\ 10-11 muscle bundles. Proboscis about i the length of body. 



T. hupferi Fischer. 

 6'. Forms possessing 2 pairs of nephridia. 

 c". Longitudinal muscle continuous. 



d\ Length of proboscis 3 to 4 times the length of body when expanded. 



T. neptuEii Gaertner. 



