838 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [120] 



Dimensions. 



No. 1. 



No. 2. 



No. 3. 



No. 4. 



Length of head and neck 



mm. 

 1.10 

 0.20 

 0.14 

 0.20 

 0.50 

 0.10 

 0.10 



mm. 

 1.00 

 0.22 

 0.10 

 0.16 

 0.40 

 0.12 

 0.08 



mm. 

 1.00 



0.10 

 0.16 

 0.40 

 0.12 

 0.12 



mm. 

 1.30 



Breadth of head 



0.32 



Breadth of neck 



0.14 



Breadth of neck at contractile bulbs 



0.26 



Length of contractile bulbs 



0.60 



Length of first segment 



0.12 



Breadth of first segment 



0.20 







In all the above, except No. 4, the first two segments were rounded 

 at the extremities so as to appear distinctly beaded. 



A few mature segments associated with this lot measured as much 

 as 1.6 mm in length and 0.3 ram in breadth. They are elongated, oppressed 

 at the ends, tapering gently towards the posterior end, with somewhat 

 irregular sinuous outline. 



The proboscides are evidently very long, since, although none were 

 seen fully everted, they could in some instances be traced back, not 

 only through the entire length of the sheaths, but into the contractile 

 bulbs themselves. 



The following measurements of proboscides and hooks are from alco- 

 holic specimens : 



Dimensions. 



Diameter of tumid base of proboscis 



Length of hooks in front of tumid base 



Maximum length of hooks near base 



Breadth of largest hooks 



Diameter of proboscis in front of tumid base. 



No. 1. 



mm. 

 0.027 

 0.003 

 0.006 



0.020 



No. 2. 



mm. 



0.022 



0.016 



No. 3. 



mm. 



0.025 



0.003 



0.006 



0.001 



0.017 



No. 4. 



mm. 

 0.019 

 0.005 

 0.007 

 0.001 

 0.014 



In all cases, with one exception, these specimens with the fine hooks 

 on the proboscides had mouiliform anterior segments, usually two in 

 number. Conversely the coarser hooked proboscides of R. hispidum 

 were associated with indistinct, squarish, anterior segments. 



This species is evidently near R. heteromerum Diesing, with which it 

 agrees closely, with the exception of that very important character, the 

 length of the proboscides. According to DiesiDg's description, the pro- 

 boscides are scarcely longer than the bothria. Diesing's species is made 

 to accommodate Wagener's Tetrarhynchus trygonis brueconis. Wage- 

 ner's figure of this species represents a worm with short proboscides, or, 

 what is more likely, with long proboscides partly everted. In the ab- 

 sence of a better description of the hooks on the proboscides than is 

 given for R. heteromerum, it is not possible to refer any of these small 

 Rhynchobothria from Trygon centrum to that species. 



