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XX. — On Haemonais laurentii, n. sp., a Representative of a little-known Genus 

 of Naididae. By J. Stephenson, D.Sc, Professor of Zoology, Government 

 College, Lahore. 



(MS. received January 13, 1915. Read February 15, 1915. Issued separately May 11, 1915.) 



[Plate LXXIX.] 



In the year 1900 Bretscher (l) published a short account of a new aquatic 

 Oligochsete belonging to the family Naididse, which was assigned by him to a new 

 genus, Hasmonais, under the name H. ivaldvogeli. Its chief peculiarity lay in the 

 complicated blood-vascular system, to an account of which Bretscher devotes about 

 half of his description. No further account of any representative of the genus has 

 since appeared. 



Some months ago I was surprised to find, in Lahore, specimens which were 

 certainly referable to the same genus as the Swiss worms, though manifesting a few 

 differences, sufficient to distinguish them as a separate species. Since my first 

 discovery of the present form I have had the advantage, which did not fall to 

 Bretscher's lot, of being able to observe sexual individuals ; and as the worms are 

 remarkable in other respects than that of the vascular system, and since moreover 

 the somewhat curt description which he gives is perhaps scarcely sufficient to satisfy 

 legitimate curiosity in regard to a new genus, I give below a fairly complete account 

 of the Lahore specimens. 



My description of the vascular rings and their branches in the anterior part of 

 the body differs somewhat from Bretscher's, mainly in being less detailed. At the 

 time that I had the living worms under observation (in which alone the vascular 

 system can be traced in detail), Bretscher's original paper was not available in 

 Lahore ; I was therefore unable to compare my specimens with his description. But 

 I am inclined to doubt if much more could have been seen, with any degree of 

 certainty, than is given below ; the present species seems to be considerably larger, 

 and therefore more opaque, than Bretscher's. It may be added that Bretscher 

 does not note, for H. ivaldvogeli, the curious fact that the dorsal vessel is not actually 

 dorsal, but runs along the left side of the intestine from the posterior end as far as 

 segment vi. 



Hsemonais laurentii, sp. nov. 



A number of specimens of this species were obtained from the duck-pond in the 

 Lawrence Gardens, Lahore, towards the end of March 1914. 



The maximum length of the specimens when extended was about 20 mm. The 

 anterior end of the animal tapers gradually ; the prostomium is triangular, with a 



TRANS. ROY. SOC. EDIN., VOL. L, PART IV (NO. 20). 106 



