Academic Editor's comments (Anna Stepanova):

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N.B. These are the comments made by the academic editor when reviewing an earlier version of this paper. Prior to publication the manuscript has been revised in light of these comments and to address other editorial requirements.
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The paper is well written and satisfies all the requirements of the PLoS ONE publishing.

1) What are the main claims of the paper?
Authors studied in detail and revised the original material (carapaces and soft body) and some additional material from the type locality of species C. mariae that was considered lost.

2) Are the claims properly placed in the context of the previous literature?
The original description of C. mariae contained only the description of the carapace. The present paper suppliments the original description and illustrates the original material together with recently obtained material from the type locality.

3) Do the experimental data support the claims? If not, what other evidence is required?
yes

4) Who would find this paper of interest? And why?
The paper is of great interest for bilogists and micropaleontologists studying the taxonomy of Myodocopid ostracods. This work clarifies the taxonomy of the genus Cylindroleberis and illustrates the holotype specimens of the type species C. mariae that were considered lost.

5) In what further directions would it be useful to take the current research?
The ecological aspects are not considered in this work. It would be interesting for a wide range of researchers to learn about the habitats of discussed species for further use in paleoenvironmental studies.

6) Is the manuscript written clearly enough that it is understandable to non-specialists? If not, how could it be improved?
The manuscript is well written, but since it depicts a very particular and highly specialized subject, it can hardly be well understood by non-ostracodologists.

The taxonomy papers are mostly oriented on specialists, so the only thing worth improving is the part where the authors could introduce the data on the ecology of the species, which can be useful for a wider range of researchers.

7) Have the authors provided adequate proof for their claims without overselling them?
yes

8) Have the authors treated the previous literature fairly?
yes

9) Does the paper offer enough details of its methodology that its experiments could be reproduced?
No, the section "material and methods" should be supplemented with more details: how, when, by whom the additional material was collected, where exactly, what did the samples represent? How many specimens were used for the description?

10) PLoS ONE encourages authors to publish detailed protocols as supporting information online. Do any particular methods used in the manuscript warrant such a protocol?
no

Other comments and suggestions.
1) I suggest to re-organize the paper in the following fashion: Title, Authors, Affiliations, Abstract, Introduction, Methods, Results, Discussion, Acknowledgments, References, Figure Legends, and Tables.

It is important to supplement the section "material and methods" as recommended above and to place it before the "Results".

2) Introduction (3 and 4 paragraphs) contains the explanation why authors rejected the previously designated synonyms of C. mariae, as well as other details that has to be placed in the "Discussion" section.

3) In the description of the genus Cylindroleberis the authors revise the taxonomic composition of this genus and state that C. vicina must be considered a separate species instead of a subspecies C. grimaldi vicina as it was before. Listing the diagnostic features of the species C. vicina, which is distinguished from C.grimaldi by authors, they only mention the difference in size and appendages' morphology. I, myself being a paleontologist, find it extremely inconvenient when species are indistinguishable using only the carapace morphology. Besides, the difference in appendages' morphology seems to be not pronounced and variable within this genus.

4) The description of C. mariae must be more structured.
Species name
Figures in this paper
Synonyms
Holotype with type locality
Diagnosis
Description
Comparison with most similar species
Remarks (if any)
Material
Distribution, together with stratigraphical range if known