AGASSIZ AND CLARK: REPORT ON ECHINI. 129 



Laganum diploporum A. Ag. and Clark. 

 This interesting species resembles strigatum A. Ag. and CI. in the form of the 

 test and the shape of the petals. But the sutures between the plates are scarcely 

 visible, and the color is commonly light green, often yellowish, sometimes brown- 

 ish. The striking characteristic, however, is the presence of six genital pores, two 

 of which are in the posterior iuterambulacrum. Of the 54 specimens with an un- 

 injured abactinal system, 34 show the six pores plainly; of the remaining 20, 17 

 are under 20 mm. in length, and most of them have no genital pores, at least in 

 the posterior interambulacrum. One specimen, 22 mm. long, has five small pores, 

 but the one in the posterior interambulacrum is at the extreme right hand side of 

 that area. A specimen 37 mm. long, and another 43 mm., apparently have only 

 one pore in the posterior interambulacrum, but under the microscope it becomes 

 evident that this pore is formed by the fusion of two. The steps in the history of 

 such a fusion are all shown in the large series of specimens available. The great 

 majority of the specimens are circular or nearly so, but some of the smaller ones 

 are slightly elongated. The most elongated specimen measures 28 by 26 mm., 

 while the largest ones are 38 X 38.5, 40 X 42, and 43 X 42. The smallest is 

 only 8 mm. in diameter. 

 Station 4885. Between Nagasaki and Kagoshima, Japan, 53 fathoms. 



" 4888. Between Nagasaki and Kagoshima, Japan, 71 fathoms. 



" 4893. Southwest of Goto Islands, Japan, 95-106 fathoms. 



" 4895. Southwest of Goto Islands, Japan, 95 fathoms. 



" 4902. Southwest of Goto Islands, Japan, 139 fathoms. 



" 4904. Southwest of Goto Islands, Japan, 107 fathoms. 



" 4933. Off Kagoshima Gulf, Japan, 152 fathoms. 



" 4934. Off Kagoshima Gulf, Japan, 103-152 fathoms. 



" 4937. Off Kagoshima Gulf, Japan, 58 fathoms. 



" 5055. Suruga Gulf, Japan, 124 fathoms. 



" 5070. Suruga Gulf, Japan, 108 fathoms. 



" 5092. Off Gulf of Tokyo, Japan, 70 fathoms. 

 Fifty-six specimens. 



SCUTELLIDAE Agassiz. 

 Echinarachnius excentricus Val. 

 Scutella excentrica Esehscholtz, 1829. Zool. Atl., PI. 20, fig. 2. 

 Echinarachnius excentricus Valenciennes, 1846. Voy. Venus. Zooph., PI. 10. 



There is a good series of twenty-four specimens of this curious species from 

 Union Bay, Bayne Island, British Columbia. 



Echinarachnius mirabilis A. Ag. 



Scaphcchinus mirabilis Barnard Mss., A. Agassiz, 1863. Proc. Acad. Nat. Sei., 



Phila., p. 359. 

 Echinarachnius mirabilis A. Agassiz, 1872. Rev. Ech., Pt. 1, p. 107. 



There are numerous sand-dollars in the collection, which appear to belong to 

 this species. 



vol. li. — No. 5 9 



