236 bulletin: museum of comparative zoology. 



Color. — From the preceding table it is readily seen that 9 of the 

 21 s])ecies represented have a prevailing color of red or brownish on 

 the dorsal surface, while 4 are whitish or very pale in color, 3 are 

 yellowish or orange, 3 are conspicuously mottled, and in 3 species 

 the color in life is unknown. 



Ocelli. — The smallest number of ocelli found in any of these 

 species when mature is 8, while in another form {A. formidabiUs) 

 as many as '250 ocelli may occur. The average number of the 17 

 species in which the ocelli have been carefully obsened is a])])roxi- 

 mately 40, a number agreeing fairly well with the average number 

 found in both the New England and the European forms. 



iStylet and basis. — In regard to the relative length of the central 

 stylet and its basis, there are 7 species in which both stylet and basis 

 are of approximately equal length, and three others in which the 

 basis is but a little longer than the stylet. In a single form (^1. 

 tigrinus) the stylet is but half as long as the basis, and in another 

 species {A. 77iacracanthus) , where the basis becomes fully a milli- 

 meter in length, the stylet is but one third as long. In one form 

 {A. fulvus) the stylet is a third longer than basis, in another [A. 

 hhnaculatus) it is twice as long as basis, while in a third species (^4. 

 punctatulus) the stylet is two and one fourth times the length of 

 basis. In 6 forms the armature of the proboscis is as yet but incom- 

 pletely described or wholly unknown. 



Accessory stylets. — In at least 13 of the 21 species the occurrence 

 of more than two pouches of accessory stylets must be regarded 

 as an abnormality ; a single species (^4. angidatus) has four occa- 

 sionally, though usually but two, and while the Alaska specimens of 

 A. bimacidatus have commonly four lateral pouches, those from the 

 coast of California usually haAe but two. A single species (^4. 

 imparis^nnosus) has almost invariably three of these pouches, a 

 number characteristic of only one other species in the world, so far 

 as is known. One forin [A. formidabllis) is proAaded with from 

 six to twelve lateral pouches, the larger of these numbers being 

 equalled in but a single other known species^ from any part of the 

 world, although one other species has seven and another eight. 



Proboscidial nerves. — Of the 12 forms in which the number of 

 proboscidial nerves is accurately known, the smallest number 



"^ A. spinosissimus Burger, from the island of South Georgia. 



