IQI5-] Fauna of the Chilka Lake : Coelenterates. 85 



those from off Satpara in the latter month. At both seasons some individuals were 

 sexually mature. The species is not markedly gregarious. 



Genus Pelocoetes, nov. 



This genus is closely allied to Phytocoetes and may be diagnosed as follows : — 

 Thin- walled Metridiinae without a collar, with a vermiform column, with 

 the basal disk much reduced, with the aboral extremity capable of assuming 

 a physa-like appearance and shape, with the majority of the tentacles 

 arranged in groups each of which is placed on a flattened pedicel or out- 

 growth from the reduced oral disk ; the tentacles slender, thin-walled and 

 not very highly contractile; the oral disk not retractile. 



In the structure of its body-wall the single species of Pelocoetes closely resembles 

 Phytocoetes, but the circular muscle-sheath is even stronger and has a more intimate 

 relationship with the endoderm, with which it interdigitates when highly contracted 

 (pi. vii, fig. 3Ô). Moreover, there is a considerable region on the upper part of the 

 column in which this muscle is to some extent differentiated, being more powerful 

 and more readily thrown into physiologically independent folds than elsewhere and 

 occasionally being associated with a few scattered muscle-spaces. This region 

 does not extend upwards quite as far as the base of the oral disk, but otherwise is 

 approximately co-terminous with the stomodaeum. There is no separate sphincter. 

 The nervous layer of the mesogloea is particularly well differentiated. 



The animal lives buried in mud and its vermiform column, plainly correlated 

 with this mode of life, is not so protean as that of Phytocoetes. 



The tentacles are more numerous than in the allied genus, but variable in num- 

 ber. There is an inner circle of twelve solitary tentacles and an outer circle of 

 twelve pedicellate groups ; but the number in each group varies considerably. 



The outer wall of the column is for the most part smooth, but bears a certain 

 number of small vesicular swellings on the upper part. The cinclides are arranged 

 definitely in vertical lines on the upper muscular region. 



There are more incomplete mesenteries in Pelocoetes than in Phytocoetes, but 

 fewer than is usual in Metridium, the actual number in P. exul being 36. None of 

 these are situated in the intramesenterial spaces. Both internal and external mesen- 

 terial stomata may be present, but, as in Phytocoetes, their size, shape and position 

 are very variable. Speaking generally, the mesenterial filaments are comparatively 

 well developed in Pelocoetes; some of the incomplete mesenteries are occasionally 

 fertile; the acontia are long and relatively stout and are normally present on all 

 the fertile mesenteries. The animal is monoecious and protogynous. 



The one species known occurs in the Gangetic delta and the Chilka Lake and has 

 been found only in brackish water. 



