WITH NOTES ON THE WEST INDIAN SPECIES. 227 



Genus. BALANOGLOSSUS (Delle Chiaje). 

 With the characters of the family. 



Subgenus 1. Balanoglossus s. str. Spengel. 



Proboscis short ; proboscis-pores paired ; peripharyngeal spaces absent ; medial gonads 

 present. 



B. kupfferi v. Willemoes-Suhm. B. canadensis Spengel. 



Subgenus 2. Dolichoglossus Spengel. 



Proboscis very long ; proboscis-pore unpaired ; peripharyngeal spaces^ present ; medial 

 gonads absent. 



B. kowalevskii A, Agassiz. B. mereschkowskii Nic. Wagner. B. sulcatus Spengel. 



SYSTEMATIC DESCRIPTION OF SPECIES-. 

 Family. PTYCHODERIDAE. 

 Genus. Ptychodera. 



Subgenus 1. Chlamydothorax. 



1. Ptychodera flava Eschscholtz. 



Eschscholtz, Fr.' (182.5) Bericht liber die zoologische Ausbeute der Reise von 

 Kronstadt bis St Peter und Paul. Oken's Isis, p. 740. 



Spengel, J. W. (1893), Die Enteropneusten (Monograph, p. 190). 



Willey, A. (1897), On Ptychodera flava Esch., Q. J. M. S., Vol. XL., p. 16.5. 



Hill, J. P. (1897—8), The Enteropneusta of Funafuti, Memoirs Aust. Mus. iii. 

 p. 205 and p. 335. 



Spengel points out that this was the first Enteropneust that was ever mentioned 

 in literature, the original description and name having fallen into complete oblivion 

 until rescued by Carus in his " Prodromus Faunae Mediterraneae." My observations 

 upon this form, as a result of which I showed that it belongs to the subgenus 

 Chlamydothorax, were the first to be made since 1825. It is closely allied to its 

 congeners, Pt. erythraea Spengel and Pt. hahamensis Spengel, from both of which it 

 differs in certain minor details, especially in the matter of the proboscis-pores. 



1 The peripharyngeal spaces, as described by Spengel in B. kowalevshii, contain both cii'cular and longitu- 

 dinal muscles. In all other cases where they occur, they contain only circular or transverse muscles. 



- The species of Enteropneusta can usually be distinguished by external characters alone. When a species 

 has once been recognised as distinct, its internal anatomy must be described for itself apart, because nearly 

 allied species often differ very much in details of organisation. No two individuals of a species are exactly alike. 



^ For this reference I am indebted to Spengel's Monograph. 



