246 1>R JOHN RENN1E AND MR ALEXANDER REID ON 



The scolex is of distinctive appearance, being long, blunt, and of almost uniform 

 width, measuring _! mm. by '75 mm. in extent. There is a pair of shallow, widely 

 gaping suckers, dorso-ventrally placed, extending the whole length, and open at both 

 ends (fig. 5). 



The mature segments are rectangular in form, with slightly undulating margin. 

 In the specimen 42 mm. long, the largest, which were terminal, measured "61 mm. long 

 by 1 '04 mm. broad. They are also relatively thick, measuring in section '61 mm. 

 dorso-ventrally. 



The cuticula and sub-cuticula are of typical appearance. Beneath the sub-cuticula 

 are the yolk follicles. These are very numerous, and in many sections, e.g. those at 

 the level of the ovary, they form a practically continuous band. The individual yolk 

 cells, which vary in form, measure on an average about '014 mm. by '017 mm. 



The shape of the ovary presents no unusual features. In a section at the level of 

 its junction with the yolk ducts it has the form of a transverse band. Posteriorly to 

 this it appears as a pair of detached, more or less rounded, and thicker masses. The 

 ovarian cells measure '017 mm. by '01 mm. 



The uterus consists of a few close coils which wind dorso-ventrally, so that in 

 section it usually has the appearance of an almost complete circle. The shelled ova 

 measure '052 mm. by "041 mm. 



The testis follicles, which occupy the greater part of the central area of the 

 proglottis, measure in their greatest dimensions "034 mm. by 'OS'S mm. 



There is a well-developed inner layer of longitudinal muscles ; the dorso-ventral 

 muscles are also well marked. 



The longitudinal nerve cords are extremely ill-defined and weak, although 

 relatively large. They are placed slightly less than one-fourth of the width of the 

 proglottis from the margin, and are slightly nearer to the ventral than the dorsal 

 surface. 



The central longitudinal excretory canals can be made out only in places. They 

 are placed at the extreme lateral margin of the central layer, next to the longitudinal 

 muscles, but, as they frequently cannot be traced in serial sections, they probably 

 anastomose a good deal. Peripheral canals are present just exterior to the yolk 

 follicles. These are most clearly visible at the lateral margins, where two or three 

 frequently occur close together. 



This form differs in most particulars from all the hitherto described species of the 

 group to which it belongs, and we have therefore classed it as new, naming it Dibothrio- 

 cephalus coatsi. It is an interesting fact that two new species should have been 

 obtained from Stenorhyncli us by the Scottish Expedition, and that D. quadratus, 

 the only form hitherto described from this host, should not have been found. 



(ROY. soc. EDIN. TRANS., VOL. XLVIII., 444.) 



