48 



THE ROYAL SOCIETY OF CANADA 



There was a certain hesitation therefore in giving a specific 

 name to the single male individual which forms the subject of the 

 present note. It presents, however, such differences from any of the 

 known male forms that it seems advisable that 

 it should receive a distinctive name, even though 

 the possibility exists that it may prove to belong 

 to one of the species of which at present only 

 the female is known. I would suggest for it the 

 name M. canadensis. 



The length of the body was somewhat over 

 1-44 mm., an exact length being difficult to 

 obtain owing to the last three segments being 

 bent dorsally at a rather sharp angle. As is usual 

 in the Monstrillidœ the first thoracic segment is 

 united with the cephalic portion to form a céph- 

 alothorax (fig. I) which terminates in the middle 

 line anteriorly in a blunt point and broadens out 

 posteriorly in the region of the first thoracic 

 segment. The mouth is situated a little anterior 

 to the middle of its ventral surface. It is 

 followed by three thoracic segments of about the 

 samiC antero-posterior measurements, that of the 

 first of the three being slightly less than those of 

 Fig. 1. Monstrilla cana- the other two, but the width diminishes from 

 ?'"l'^u_^''L"î_°!^°''7 before backwards. The fifth thoracic segment 

 is much narrower than the fourth and about 

 equal to the first abdominal, from which it is 

 apparently incompletely separated. 

 The abdomen consists of four seg- 

 ments; the first or genital segment 

 is prolonged ventrally into a strong, 

 cylindrical genital appendage (figs. 

 2 and 3), which broadens out at its 

 extremity into two roughened lobe- 

 like processes which project laterally 

 and dorsally, the notch leading to 

 the genital orifice being guarded on 

 either side by about three short 

 spines. The remaining abdominal 

 segments (fig. 4) are narrower than 

 the first, the third being slightly 



from the dorsal sur- 

 face. Male. 



Fig. 2. Monstrilla 

 canadensis. Geni- 

 tal segment of 

 male from the shorter than the second and the 



side. fourth about half as long as the 



Fig. 3. Monstrilla 

 canadensis. Geni- 

 tal segment of 

 male, from the 

 ventral surface. 



