172 
Memoirs of the Indian Museum. 
[Voi,. II, 
Description of the Types. 
In their gross structure the twenty-one specimens resemble one another and 
conform to the original description of the genus ; they differ from one another in two 
respects, firstly, in the breadth of the disk' secondly, in the form and arrangement of 
the dermal ossicles. The variation in the breadth can be studied by measurement 
The length of each specimen was measured from the snout to the base of the tail fin. 
Broad 
Medium 
N arr ow 
A BCD 
Fig. 7. — Proportion of breadth to length in 21 specimens of Malthopsis of communities A, B, C and 
D; O = orderb^ x = disorderly. 
The greatest l^readth of the body was recorded as the distance between the most 
prominent parts of the subopercular spines. Measurements were taken to the 
nearest half-millimetre. The mea.surements are shown in the table at p. 176. The 
breadths are also displayed as percentages of the lengths by lines of proportionate 
length in text-fig. 7. This diagram shows that as regards breadth the specimens 
fall into three groups, the members of which may be spoken of as narrow, medium 
