183G. ] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 563 



The thoracic uuciui have from eighteen to twenty teeth ; the abdom- 

 inal, eleven to thirteen. The capillary setae from the abdomen are a 

 little more enlarged at the end. 



Length, OO""™ ; breadth, 0'"'", in alcoholic specimens. No color re- 

 mains. 



Collected at Vera Cruz. Teste Seiior J. G. Aguilera (999). 



Spirobranchus dendropoma Morcli. 



(Plate xxiv, figs. 57, 58. Plate xxv, figs. 50-56.) 



Spirobranchus dendropoma Morcb, Rev. Crit. Serp., j*. 60, 1863. 

 Cijmospira litigera Quatrefages, Hist. Nat. des Ann., tome ii, p. 545, 1865. 



Many specimens of this species were collected at St. Thomas, Jamaica, 

 and Curagao. They- agree quite well with Morch's description except 

 that the horns, five or six in number, are situated nearer the center 

 than he describes them. 



The branchiae differ from the two preceding species of the genus in 

 having but one turn on a circular rather than on a spiral base, and in 

 the structure of the branchial filaments, which have a cirrus at the base 

 of the free portion (fig. 50). 



While in these respects it differs from the leading species of the genus, 

 the structure of the opercula and the form of the setoe and unciui show 

 it to be closely related to it. The opercula vary in shape, and range in 

 color from dark blue to white. The horns of some of the larger speci- 

 mens (fig. 53) are short and stumpy, while others are long and have 

 numerous branches (figs. 51 and 52). Specimens with large horns have, 

 as a rule, more slender peduncles. The digital processes on the inner 

 margin of the wings of the peduncles are often well marked. 



No unbroken specimens of the collar-setje were found. The markings 

 on the head of the main shaft are more distinct than those on similar 

 setae of S. giganteus (fig. 54.) 



The uncini of the thorax are similar to those of the abdomen but 

 larger, and average one or two teeth more, the former having from 

 twelve to fifteen, and the latter from ten to thirteen, according to their 

 position in the row (figs. 55 and 56). The abdominal setae are scarcely 

 distinguishable from those of the preceding species (fig. 57). 



The specimens when first collected were placed in strong alcohol, and 

 still retain some color, as is often the case under these circumstances. 



The branchiae vary from a light to a dark blue banded with white. 

 The lamellae of the thorax are in most cases a dark violet-blue. The 

 thorax and anterior part of the abdomen are dark. 



Length of large specimens, 40""" ; breadth, 2.5™™. 



In tubes 5 coral reefs; shallow water (967, 968, and 977). 



