322 CEYLON PEARL OYSTER REPORT. 



ridges, on which the siphonozooids are found. Their arrangement cannot be exactly 

 ascertained, hut they seem to form an interrupted line on each of the ridges, and also 

 occur either singly or in small groups below each pinnule. 



The polyps on the separated parts vary from barrel- to flask-shape in the retracted 

 condition, and measure in this state from 0'5 millim. by 0'4 millim. to 0'65 millim. by 

 0'4 millim. In their expanded condition they are more cylindrical in shape and 

 measure 0'9 millim. by 0'4 millim. They still present a slightly swollen appearance 

 about the middle of their length. 



The six fragments represent parts of the rachides of at least three different 

 specimens. In no case is there any part of the stalk left, so that it is impossible to 

 give any idea of its shape and size. 



Locality : Trincomalee. 



FAMILY: PENNATULID^E. 

 Halisceptrum periyense, n. sp. 



The collection included a couple of specimens of what appears to be a new species 

 of Halisceptrum. Both specimens were complete and the natural colour is recorded 

 by Professor HERDMAN as pink and white. 



The lower portion of the stalk is curved and stands at right angles to the axis of 

 the rachis, with its lower extremity marked by a ball-shaped swelling. The stalk 

 passes almost imperceptibly into the lower portion of the rachis, which forms a long 

 spindle-shaped swelling marked by two narrow V-shaped lines of pores, one on each 

 lateral surface. The upper part of the rachis bears the pinnules, which show a 

 marked difference in appearance. On the upper portion they are fairly large and 

 show well-marked polyps on a wavy outline, while on the lower part they are 

 reduced to straight ridges across the lateral faces of the rachis. The proportion of 

 the mature to the immature pinnules is rather striking, there being in one specimen 

 14 mature to 53 immature, and in another 10 mature to 36 immature. 



The piSnules in the immature state have the polyps arranged in one row, but soon 

 the pinnule begins to get folded and the polyps begin to alternate, thus giving the 

 appearance of multiple rows of polyps. The distance between the origins of the 

 pinnules is 2 '5 millims. in the case of the mature, but the immature lie almost 

 touching one another. The pinnules are translucent, and they show a stringy 

 appearance when held between the eye and the light. 



The prorachidial surface of the rachis is free from pinnules and is marked by a 

 distinct narrow groove. This groove fades away and disappears entirely between 

 the immature polyps. 



We add a table of measurements of the two specimens. There is in each a single 

 row of polyps on the pinnules, but they alternate in arrangement so as to appear like 

 two or more rows. 



