124 CEYLON PEARL OYSTER REPORT. 



Mucronella coccinea, Abild. 

 Localities : Gulf of Manaar ; and off Galle. 



Mucronella tubulosa, Hincks (3). 



In the Ceylon specimens, which I believe to belong to this species, there is an 

 enormous development of the central mucro, which is here long and spinous ; there is 

 also an avicularium on the inner side of this, either at its base, lying in front of the 

 primary orifice, or at varying heights up this process, always transversely placed 

 and with a sharp curved beak, but varying in size. 



These points add to the resemblance between M. tubulosa and Rhyncopora longi- 

 spinosa, which Miss Jelly regards as synonymous, but there is missing still, in these 

 specimens, the uncinate process of Rhyncopora, unless the curved beak of the 

 avicularium takes the place of this. In the faint indication of a sinus of the primary 

 orifice, the spinous mucro and markings of the ooecia, there is a likeness to a species 

 of quite another genus, i.e., Cellepora longirostris, MacGillivray, as described by 

 Miss Philipps (25). 



Localities : Off Trincomalee ; off Mount Lavinia ; Navakaddu Paar and elsewhere 

 in the Gulf of Manaar. 



Mucronella thenardii, Aud. Plate, fig. 15. 



The cross-shaped process, situated below the orifice of the zocecium in this species, 

 is greatly developed (see fig. 15). Its upright portion is often occupied by a large 

 spatulate avicularium, and, where this is so, one of the arms of the cross is missing, 

 giving a one-sided appearance to the process. Sometimes the arms are duplicated, 

 one pair below the other, and they are always much branched, each branch bearing a 

 small, rounded aviculariurn on its summit. Slender, spinous processes, resembling the 

 branches in size, are scattered over the front wall and round the margin of the orifice 

 of the zooecium, and there are sometimes ordinary spines, from two to five in number. 



There is a strong resemblance between the characters of this species and those of 

 M. aviculifera, Hincks (14). The slender, spinous, aviculiferous processes are present 

 there, but the cross-shaped mucro is only represented by a small simple mucro, and 

 there are large, lateral avicularia. There is, however, much variation in form and 

 position of the avicularia and of the processes which carry them, even in one small 

 specimen of the present collection, so that it seems possible that the differences 

 represent various stages in the development of one and the same species. 



Localities : Gulf of Manaar ; and off Galle. 



Mucronella vultur, Hincks (7). 



There are in the present collection specimens having all the important character- 

 istics of M. vultur, as described by Hincks (7) and MacGillivray (23) with this 

 exception, that the avicularium on the central mucro has a rounded, instead of a 



