392 Mr. T. D. A. CockereW— Descriptions and 



EXPLANATION OF THE PLATES. 



List of Abbreviations employed. 



owf. CO?., anterior ca'lom ; ax., axial sinus; cct., ectoderm; hist., a 

 spot on the pre(>ral lobe ui.dergoing liistolysis ; hi/d., left liydrocoele ; 

 I.-V., its five primary lobes ; l.p.c, left posterior ccelom ; l.'p.'c.', its rigbt 

 ventral extension; mes., mesenchyme ; muse, muscular tissue developing 

 from the wall of the peribajmal canal ; nerv., nervous fibrils ; per., peri- 

 toneum ; ph., rudiments of the perihoemal spaces ; ph. 1-5, that between 

 lobes I. and V. of the hydroccele ; ph. 1-2, that between lobes I. and 11. 

 of the hydroccele ; pr.yerm., primitive germ-ceUs ; r.p.c., right poste- 

 rior coelom ; st.c., stone-canal. 



Plate XIL 



Fig. A. Three embryos adhering by their preoral lobes. 



Fig. B. An unfertilized e§^. 



Fig. 0. The youngest embryo in the collection, showing primary lobes of 



the hydroccele. 

 Fig. D. A slightly older embryo. The rudiments of the arms appear as 



bosses above the lobes of the hydroccele. 

 Fig. E. The oldest embryo in the collection. The pentagonal form is 



clear, and the rudiments of the tube-feet have appeared. 

 Fig. F. Transverse section of a comparatively young embryo, showing 



relations of ccelomic cavities, the stone-canal as open groove, 



and the perihjemal cavities arising as evaginations of the 



ccelom. 



Plate XIII. 



Fig. G. Portion of another transverse seeti'^n of an embryo about the 

 same age as that represented in PI. XII. fig. F, showing the 

 formation of the axial sinus by constriction from the anterior 

 ccelom. 



Fig. H. Another transverse section, showing gut-wall and its relation to 

 the yolk. 



Fig. I. Section, more highly magnified, of a small portion of the ventral 

 body-wall, showing the relations of a lobe of the hydroccele to 

 the perihsemal space and the ectoderm. The beginnings of 

 nervous and muscular tissue are seen. 



Fig. J. Section, highly magnified, of a small portion of the dorsal bodv- 

 wall, showing yolk-globules in the dermis and the first rudi- 

 ment {pr.gtrm.) of the genital stolon or " ovoid gland." 



Zoological Laboratory, McGill University. 

 June 1905. 



XLV. — Descriptions and Records of Bees. — TV. 

 By T. D. A. CocKERELL^ Uuiversity of Colorado. 



Bombus sumairensis, sp. n. 

 ? . — Length about 18 mm. 



Head elongate, narrow, the greater part o£ the clypeus, 

 which is smooth and shining, below the level of the* eyes ; 



