344 MR. J. R, HENDERSON — A CONTRIBUTION 



Silavaturai Par, a female with ova {Thurston). 



In this specimen the carapace is yellowish in colour, mottled with red on the gastric 

 area and at the sides of the cardiac area. The carapace, which is overgrown with 

 sponges and ascidians, measures 35 mm. in length and 20 mm. in breadth ; the rostral 

 spines are 11 mm. long, and measured between their apices 55 mm. 



Distribution. Mergui, Malay Archipelago. 



12. Hyastenus convexus, Miers. 



H. convexus, Miers, ' Alert' Crust, p. 196, pi. xviii. fig. B (1884). 



Gulf of Martaban, a female with ova (Oates). 



I refer this with some doubt to the present species. It agrees in having the gastric 

 area of the carapace smooth and very convex, the cardiac area also smooth and but slightly 

 less convex. But the rostral spines are somewhat less divergent, and a small epibranchial 

 spine is present, while according to Miers there is none. In other respects it agrees 

 with the description, and it is apparently identical with dried specimens from Penang, in 

 the British Museum, labelled by Miers " Hyastenus convexus, Miers, var." The carapace 

 measures 13 mm. long (not including the rostral spines), and the rostral spines 6 mm. long. 



Distribution. N.E. Australia (Miers) ; Penang (Brit. Mus.). 



13. Hyastenus Hilgendor.fi, De Man. 



H. Hilgendorfi, De Man, Mergui Crust, p. 14, pi. i. figs. 3, 4 (1887). 



Rameswaram, Tuticorin, Cheval Par (Thurston). Not uncommon on the reef at 

 Rameswaram (J. R. H.). 



Allied to H. Pleione (Herbst), from which it may be distinguished by the absence of 

 median spines from the dorsal surface of the carapace, and the presence of only two 

 tubercles on the anterior gastric region. The rostral spines are much longer in adult 

 males than in females and young males. Most of the specimens are overgrown with 

 hydroids and sponges. 



The largest specimen (an adult male) has the carapace 34 mm. in total length (including 

 rostral spines), and the rostral spines measured from the level of the anterior orbital 

 margin 15 mm. long. 



Distribution. Mergui (De Man). 



14. Hyastenus Brockii, De Man. 



H. Brockii, De Man, Brock's Crust, p. 221, taf. vii. fig. 1 (1888). 



Gulf of Martaban (Oates). 



In a single male specimen which I refer to this species (carapace 85 mm. long, 6 mm. 

 broad, length of rostrum 10 mm.) the cardiac area of the carapace is more elevated than 

 is represented in De Man's figure. It is chiefly characterized by its very long and 

 slender rostral spines, which are longer even than the carapace. 



Distribution. Amboina. 



