HABITS OF THALASSINA ANOMALA. 215 



Through the studj' of the structure of preserved speeimens, Bate 

 surlnised that Thalassina was able to live in iDOorly aerated water, 

 and its habits are such that tliis ability would often he of advantage. 

 It possesses an adaptation that is probably for this purpose, that is, 

 the branchiostegites are movable on the dorsal portion of the carapace 

 by a sort of flexible hinge-joint. An individual placed in a dish will 

 often move the sides of the carapace in such a manner that it resembles 

 a vertebrate gasping for breath. Such movements would serve to clear 

 the water quickly from the branchial chamber. 



Judging by an examination of the stomach contents of a medium 

 sized female captured at 11.00 in the morning of July 20 and examined 

 about two hours later, Thalassina is a vegetarian. This stomach con- 

 tained a little fine silt, many bits of vegetable tissue (apparently largely 

 from the stems of vascular plants), a root tip, and a small grass plant 

 bearing several leaves and roots. These things indicate that the food 

 came largely from the pasture land at the edge of the estuary, for 

 the most careful examination failed to reveal any algae. Algse are 

 always abundant in the stomachs of the fiddler crabs that dig their 

 holes beside those of Thalassinn and feed over the wet mud-fiats during 

 the day. 



The Thalassina is extremely shy. Most of its burrows are closed 

 during the day, but more of them are open on rainy or cloudy days 

 tlian when the weather is clear. When handled or placed on the ground 

 this crustacean is slow moving and cautious rather than j)ugnaceous, 

 attempting to hide or to creep away. ■ It is apparently nocturnal or 

 becomes active in the twilight, for fresh mud is usually seen at the 

 mouth of burrows in the morning, rarely in the afternoon. Though 

 Thalassina depends largely on its secretive habits to protect it from its 

 foes, once it is in the hand of its enemy the many spines on the surface 

 of the body and legs form an admirable adaptation for escape. Those 

 on the body all point toward the anterior end and when in the grasp 

 of an enemy serve to prevent the body from slipping forward but facil- 

 itate movement in the opposite direction. It is surprising how hard 

 it is to hold an animal that pushes your hand forward frantically with 

 its legs; the spines do not allow the lingers to regain their hold easily. 

 Hence Thalassinu often slips to the ground and backs into the nearest 

 burrow. 



The Filipinos assert that the palatal- makes sounds, and they attempt 

 to imitate them by making a popping noise with the tongue, similar to 

 that made by the cork of a beer bottle as it is withdrawn. The writer 

 has often heard such sounds when among the Thalassina buiTows, and has 

 produced a similar sound hj nibbing that animal's first leg along the 

 curved row of spines on each side of carapace, but has never seen this 

 species stridulate. 



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