On the NepJiridia &c. of Arenicola. 295 



(13) Halictus pseudopectoralis^ sp. n. 



2 . Length 7 millim. Black, shining ; wings greyish. 

 This so closely resembles the U.S. species allied to pectoralis 

 that it will be only separated by a comparative description. 

 The front above level of antennae is closely punctured, as in 

 the allied species. From pectoralis^ Sm. (Illinois specimen, 

 determined by Robertson), it differs by the darker wings, the 

 somewhat broader face, the much less closely punctured meso- 

 thorax, the entirely black tegul^e, the more regularly wrinkled 

 enclosure of metathorax, and the very distmct white hair- 

 patches at lateral bases of segments 2 and 3 of abdomen. 

 From quadrimaculatus, Rob., it differs by the somewhat 

 dai-ker wings, the larger head, the more sparsely punctured 

 mesothorax, the black tegulfe, and the more strongly wrinkled 

 enclosure of metathorax. From pectoraloides^ Ckll., it differs 

 principally in the strong regular longitudinal wrinkles of the 

 metathoracic enclosure, but also in the darker wings and the 

 brownish pubescence on the hind tarsi. 



In its metathorax it resembles most pectoralis^ in the sculp- 

 ture of the mesothorax pectoraloides. The median impressed 

 line of the mesothorax is very distinct. 



Paso de Telaya, March 30 ; San Rafael, March 8 and 9. 

 On Bidens and another composite. 



Mesilla, New Mexico, U.S.A., 

 Aug. 10, 1896. 



XLV. — Papers from the Gatty Marine Laboratory, St. An- 

 drews. — On the Nephridia, Reproductive Organs, and Post- 

 larval Stages of Arenicola. By H. M. Kyle, M.A., B.Sc, 

 Berry Scholar in Natural Science, University of St. An- 

 drews. 



[Plates Xm.-XV.] 



While endeavouring to work out the development of 

 Arenicola I was naturally led to examine the nephridia and 

 then the reproductive organs. Both of these have been 

 described "quite recently, by Cunningham in 1888 (4) and by 

 Benham in 1891 (1), and in this paper I cannot do more than 

 confirm their descriptions for the most part and add one or 

 two points of interest. 



On the sands of St. Andrews Bay and all round the coast 

 Arenicola is got in great abundance and in all stages — from 



21* 



