30 McMURRICH 



case in the arenicolous individuals. The extent of the protru- 

 sion of the verrucae together with the amount of contraction of 

 the column would bring about variations in the proximity of the 

 verrucae, which are frequently described as being separated from 

 one another, though in the present specimens they are so 

 closely approximated as to be in some cases more or less 

 quadrangular in outline, owing to mutual contact. So too the 

 amount of protrusion will produce variations in their size ; in 

 all the specimens of the present collection the verrucae about the 

 middle of the column are larger than those above and below, 

 but in the different individuals the size of the largest ones vary, 

 being as much as over i mm. in diameter in some specimens, 

 while in others they are less than half that size, 



I have discussed these varieties of the verrucae somewhat at 

 length because they serve to illustrate \ery pointedly the un- 

 certainty of taking external peculiarities alone as a basis for 

 specific distinctions. When I first examined the specimens of 

 the present collection I regarded the arenicolous forms as quite 

 distinct from the others and it was only after I had studied the 

 internal structure of both that I became certain of their identity. 



One other point in the external structure I may refer to 

 briefly namely, the arrangement of the tentacles. The decamer- 

 ism is fairly well pronounced, but never perfect : thus in one 

 specimen is which an accurate count was made there were 133 

 tentacles only, instead of the 160 which might be expected. The 

 variations of the tentacles however being associated with the 

 arrangement of the mesenteries, need not be discussed in detail 

 and I mention it merely on account of the importance which has 

 been assigned to it by Cunningham ('89). 



Color. — All the specimens collected were uniform in color 

 throughout the column, and were either red or orange brown 

 (the ** color of an over ripe banana " Calkins). The arenicolous 

 forms were of a bright vermilion color, with paler tentacles, and 

 their appearance when dug from the sand has been so graphic- 

 ally described by Dr. Calkins that I quote his description. "They 

 look very much like a tomato baked in bread crumbs. They 

 have the same wrinkled appearance of the skin, while the ap- 



