284 Ortmann — Crangopsis vermiformis. 



Of this specimen the body is complete, showing the 

 carapace and the whole abdomen preserved in situ. Fortu- 

 nately, the hinder and upper part of the carapace is broken 

 away, thus enabling us to see that in addition to the seven 

 abdominal segments exposed in specimens with unbroken 

 carapace, there are, in front of them, four other segments 

 present, originally covered by the hinder expansion of the cara- 

 pace, and these four (thoracic) segments are dorsally perfectly 

 closed, smooth, and uninjured, thus proving that they were not 

 connected and anchylosed with the carapace, but free dorsally. 

 These free thoracic segments are exhibited in a few other 

 specimens (Mus. No. 1597 d ), but since in the latter the abdomen 

 is not complete, their exact number cannot be determined. 



This character clearly shows that Crangopsis vermiformis 

 cannot be a Decapod. In the Decapods all the thoracic seg- 

 ments are firmly united dorsally with the carapace. Neither 

 can Crangopsis belong to the Euphausiacea, because in this 

 order only the last (fifth) thoracic segment is dorsally free, 

 while all the others are united with the carapace. In the 

 Stomatopoda the five thoracic segments are free, but they are 

 not covered by the carapace; only in the Mysidacea we have 

 the same condition as shown by Crangopsis. Thus, according 

 to this character, this genus should be placed in the order of 

 Mysidacea, and it is the first fossil form assigned to this group. 



I think, however, it would be a little rash to assume posi- 

 tively that Crangopsis belongs to that group of recent animals 

 designated as the order Mysidacea, since we know nothing of 

 the other characters of this form. It is true, the character 

 mentioned is present, among the living Malacostraca, only in 

 the order of Mysidacea, but it is a mere secondary one, the 

 principal characters being drawn from the differentiation of the 

 appendages of the body. In the fossil Crangopsis only faint 

 traces of limbs have been discovered, but their number, their 

 shape and differentiation are entirely unknown, and accordingly 

 we are at a loss to recognize the typical characters of any par- 

 ticular order of the Malacostraca ; we may even imagine that 

 Crangopsis possessed in the conformation of the thorax the 

 characters of Mysidacea, while the limbs were developed 

 according to the Decapod-type, a condition which is not alto- 

 gether impossible. Since Crangopsis belongs to the earliest 

 forms of Malacostraca, we are to expect that it belongs to a 

 primitive group, perhaps to that group which forms the origi- 

 nal stock from which all the now living Malacostraca originated. 

 But the presence of a carapace covering entirely the thorax 

 indicates that this genus belongs to the Thoracostraca, and 

 further, the fact that the four last thoracic segments are dor- 



