198 CEYLON PEARL OYSTER REPORT. 



(2) Tables in the papillae. These are much larger than those of the general 

 integument, and are not regular in shape (fig. 34). They have a similar spire 

 to the smaller tables. 



The calcareous ring is not very large, being 8 millims. long and 8 millims. broad. 

 It consists of ten pieces. The five radials are slightly notched anteriorly and are 

 bifurcated posteriorly. The posterior prolongations are composed of a number of 

 smaller pieces. The five inter-radials have no posterior prolongations and are pointed 

 anteriorly. Retractor muscles are present (fig. 35). 



There is one Polian vesicle, and no stone canal can be seen. The gonads are 

 present in two bunches one on each side of the dorsal mesentery. The right 

 respiratory tree is larger than the left. There are no Cuvierian organs. 



The presence of posterior prolongations to the calcareous ring, together with the 

 possession of retractors, prove that this form is a Dendrochirote, although the 

 tentacles are absent. 



It possesses a certain external resemblance to the genus Colochirus in the general 

 shape of the body ; in the arrangement of the pedicels in three rows on the ventral 

 surface, and of the papilla? on the dorsal surface ; and also in the presence of the five 

 valves around the mouth. 



But there is no doubt that the species is not a Colochir us, because : 



(1) The pedicels extend the entire length of the ventral sui'face (in Cohchirus they 



are absent at both ends). 



(2) The deposits, which consist entirely of tables, are different from those of the 



genus Colochirus. 



(3) The calcareous ring has posterior prolongations. 



Neither does this species agree with any other genus of the Dendrochirotie, so 

 that I feel compelled to form for it a new genus which may be defined as follows : 



Havelockia,* n. gen. 



The body is indistinctly quadrangular, and the mouth and anus are each surrounded 

 by five valves. The ambulacral appendages consist of (l) pedicels, arranged in three 

 series on the ventral surface, each series extending from the mouth to the anus, and 

 consisting of several rows of pedicels ; (2) papillae, which are scattered irregularly 

 over the bivium. 



The deposits consist entirely of tables. Each table has a spire consisting of two 

 rods, which are surmounted by three or four short blunt projections. 



The calcareous ring has posterior radial bifurcations. 



* Named after the SS. " Lady Havelock," from which Professor Hekdman worked during the greater 

 part of his expedition in the seas round Ceylon, 



