376 MRS. E. W. SEXTON ON A [Apr. 28, 



the female has been published hitherto. The figui^e given by- 

 Costa is evidently that of a female, but his specimens cannot be 

 traced. The last mention of them is in the ' Annuario ' (6),. 

 where they are referred to as forming part of the Collection of 

 Crustacea sent to the Paris Exposition, 1867. The method of 

 preservation is described, the specimens being dried and mounted 

 in glass cells. 



Though the geographical range of this species is wide, the 

 specimens taken have been few in number : Costa's specimens ; 

 the three males described in Prof. Delia Valle's work (15) ; a 

 female from the Gulf of Genoa ; two females from the Bay of 

 Biscay, one taken by the ' Pi-incesse- Alice,' and one by the 

 ' Huxley ' ; and Mr. Tattersall's six specimens, all from the 

 west coast of Ireland, three females and three males. Thanks 

 to Mr. Tattersall's kindness in permitting me to examine these 

 last and to dissect a male specimen, I have been able to satisfy 

 myself that the oral parts taken by Delia Yalle as characters 

 to differentiate the genera Guerina and Trischizostoma are 

 really identical in structure in both forms. The first maxilla, 

 in particular, which he describes as lacking the inner plate, 

 and with the palp reduced to a small and simple tubercle,, 

 will be seen to possess not only the inner plate, but a minute, 

 distinctly bi-articulate palp (PI. XV. figs. 1 & 2). These struc- 

 tures, however, are so exceedingly fragile and pellucid as to 

 render dissection very difficult. The little leaf- like palp arises 

 in a small hollow inside the margin of the outer plate, and sets 

 out at right angles to it ; when mounted for the microscope the 

 weight of the cover-glass is quite sufficient to depress it into 

 the hollow, thus giving the effect of a little tvibercle. 



The description of the male is taken principally from the Irish 

 specimen, 21'5 mm. in length ; that of the female fi-om the 

 ' Huxley' specimen, 23 mm. in length. All the measurements are 

 taken in the same way, from the tip of the I'ostrum to the tip of 

 the telson, along the medio-dorsal line. 



There is little difference between the sexes, the principal dis- 

 tinguishing characters being found in the antennas. 



The Integument is very characteristic, having the apjjearance of 

 " pitting" ; under a high power each little pit is seen to be irre- 

 gularly six-sided and fringed with sharp spines (PI. XIV. fig. 2). 



The Head is much deeper than the perteon, about as long as 

 deep ; rostrum broad, apically rounded, curving right over the 

 bases of the superior antennfe. The head is longer than the 

 first segment of the perseon (2*5 mm. to 1*5 mm.), about as long 

 as the first segment and half the second. Eyes large, dark brown 

 in colour, the pigmented masses on each side numbering not less 

 than 60 ommatidia, arranged in eight or nine transverse rows, 

 with an irregular I'ow of smaller unpigmented ommatidia entirely 

 surrounding the pigmented masses and meeting in the medio- 

 dorsal line. 

 ■ Person. — The 1st segment is the longest ; the 2nd, 3rd, and 



