5 



generic value. The eyes themselves are frequently nearly semiglobular, in Erythrops G. O. S. 

 depressed ; in the two blind species of Boreomysis G. O. S. {B. scyphops G. O. S. and B. distiti- 

 gnenda H. J. H.) and in the genera Pseudomysis G. O. S., Pseudomma G. O. S., Calyptonima 

 Tatt., Amblyops G. O. S., Bathymysis Tatt., and Paramblyops Holt & Tatt. the retina has 

 disappeared, and in the latter types the entire appendages have been strongly altered, plate- 

 shaped, in Pseudomma and Calyptomma even coalesced with each other. The eye-stalks are long 

 in some, very short in other genera. In several forms a triangular or nearly cylindrical process is 

 seen on the inner or upper side near the margin of the retina, and in Mastigophthalmus Illig 

 this process is extremely long. In some genera {Eiichatomera G. O. S., Mastigophthalmns Illig) 

 each eye has its retina divided into two eyes, sometimes considerably removed from each other 

 and always showing internal differences; in Arachnomysis Chun the eyes differ in aspect from 

 those in all other forms, according to Chun answering only to the upper section of the eyes 

 (the upper eyes) in his Brutomysis (= Etichatomcra G. O. S.). 



A n t e n n u 1 a;. — The peduncle is sometimes about equally thick in both sexes, but 

 most frequently it is conspicuously, sometimes even very much, thicker in the male than in 

 the female. But other sexual characters are of more importance. In the subfamilies Boreomysin^e, 

 Rhopalophthalminse, Gastrosaccinae, Mysidellinse and the tribe Heteromysinaj the male lobe 

 bearing the sensory setaj on the lower side of third joint is very short and knot-shaped or 

 rudimentary, while in the Siriellin?e and the Mysinje excepting Heteromysis Smith it is of 

 considerable size, thick and protruding in front, frequently even a long process. In some forms, 

 as Boreomysis G. O. S., RJiopalophthaltims Illig, Gastrosaccns Norm, and Anchialina Norm., 

 the basal part of the outer flagellum in the male is expanded on the inner side. Other differences 

 observed are of small importance. 



Antennae. — The squama is wanting in Arachnomysis Chun, Gymnerythrops n. gen. 

 and Chunomysis Holt & Tatt., very reduced in Oesaroinysis Ortm., well developed in all other 

 genera of the family. In Siriclla anomala n. sp. it shows a strong sexual difference (see below). 

 Its distal suture is observed in the large majority of forms, but it is easily and frequently over- 

 looked, and it is certainl)- of slight systematic value. On the extreme variability of the shape 

 of the squama it is not necessary to speak; frequently its size and general shape afford useful 

 generic characters, and sometimes the same features may be used as additional characters for 

 some small subfamilies, but the large specific differences in shape and furniture with seta; or 

 spines sometimes met with in forms belonging to the same genus (for instance between Amblyops 

 Crozetii Will.-Suhm and A. aiistralis G. O. S., or between Erythrops erythrophthalma Goes 

 and E. serrata G. O. S.) show that even such strong differences not unfrequently tell little or 

 nothing on the affinity among genera. 



Labrum. — In Mysidellina; this organ is very aberrant, being produced posteriorly 

 into a thin lamella divided by a deep angular incision into two considerably unequal lobes. In 

 the majority of the other genera it is a little broader than long, with the front margin very 

 convex or ansfular and the an^le itself rounded, but in the Siriellinae, the Gastrosaccinre and the 

 genus Lycomysis n. gen. it is very much longer than broad, being anteriorly produced into a 

 long, pointed process. The shape of the labrum thus seems to be a character of importance, 



